diff --git a/bin/process b/bin/process
index d5fc472..02819a7 100755
--- a/bin/process
+++ b/bin/process
@@ -7,13 +7,12 @@ require "stringio"
 
 data = File.read(ARGV[0])
 
-shipments = PlanetExpressExpress::ShipmentReader.new(PlanetExpressExpress::PRICE_LIST).read_shipments(data)
-PlanetExpressExpress::Rules.new(PlanetExpressExpress::PRICE_LIST).apply_rules(shipments)
-PlanetExpressExpress::DiscountBudget.new(PlanetExpressExpress::DISCOUNT_LIMIT).limit_discounts(shipments)
-
 output = StringIO.new
-
-PlanetExpressExpress::Formatter.new(output).format(shipments)
-
-output.rewind
-puts output.read
+PlanetExpressExpress::ShipmentReader.new(PlanetExpressExpress::PRICE_LIST).read_shipments(data) do |shipments|
+  PlanetExpressExpress::Rules.new(PlanetExpressExpress::PRICE_LIST).apply_rules(shipments)
+  PlanetExpressExpress::DiscountBudget.new(PlanetExpressExpress::DISCOUNT_LIMIT).limit_discounts(shipments)
+  PlanetExpressExpress::Formatter.new(output).format(shipments)
+  output.rewind
+  puts output.read
+  output.rewind
+end
diff --git a/lib/planet_express_express/discount_budget.rb b/lib/planet_express_express/discount_budget.rb
index 7a0fecc..0ce432d 100644
--- a/lib/planet_express_express/discount_budget.rb
+++ b/lib/planet_express_express/discount_budget.rb
@@ -5,15 +5,13 @@ module PlanetExpressExpress
     end
 
     def limit_discounts(shipments)
-      shipments[:all].each do |month|
-        available_budget = @limit_per_month
+      available_budget = @limit_per_month
 
-        month.each do |shipment|
-          if shipment.discount > available_budget
-            shipment.discount = available_budget
-          end
-          available_budget -= shipment.discount
+      shipments[:all].each do |shipment|
+        if shipment.discount > available_budget
+          shipment.discount = available_budget
         end
+        available_budget -= shipment.discount
       end
     end
   end
diff --git a/lib/planet_express_express/formatter.rb b/lib/planet_express_express/formatter.rb
index b7538f3..d6f6664 100644
--- a/lib/planet_express_express/formatter.rb
+++ b/lib/planet_express_express/formatter.rb
@@ -5,12 +5,10 @@ module PlanetExpressExpress
     end
 
     def format(shipments)
-      shipments[:all].each do |month|
-        month.each do |shipment|
-          @io.write(
-            "#{shipment.date.iso8601} #{shipment.size} #{shipment.provider} #{(shipment.price - shipment.discount).to_s.rjust(3, "0").insert(-3, ".")} #{shipment.discount.zero? ? "-" : shipment.discount.to_s.rjust(3, "0").insert(-3, ".")}\n"
-          )
-        end
+      shipments[:all].each do |shipment|
+        @io.write(
+          "#{shipment.date.iso8601} #{shipment.size} #{shipment.provider} #{(shipment.price - shipment.discount).to_s.rjust(3, "0").insert(-3, ".")} #{shipment.discount.zero? ? "-" : shipment.discount.to_s.rjust(3, "0").insert(-3, ".")}\n"
+        )
       end
     end
   end
diff --git a/lib/planet_express_express/rules.rb b/lib/planet_express_express/rules.rb
index d3ce9a3..b8ec371 100644
--- a/lib/planet_express_express/rules.rb
+++ b/lib/planet_express_express/rules.rb
@@ -15,26 +15,22 @@ module PlanetExpressExpress
 
     attr_reader :lowest_s_price
 
-    def l_rule(monthly_shipments)
-      monthly_shipments.each do |month|
-        lp_count = 0
-        month.each do |shipment|
-          next if shipment[:provider] != :LP
+    def l_rule(month)
+      lp_count = 0
+      month.each do |shipment|
+        next if shipment[:provider] != :LP
 
-          lp_count += 1
-          if lp_count == 3
-            shipment.discount = shipment.price
-            break
-          end
+        lp_count += 1
+        if lp_count == 3
+          shipment.discount = shipment.price
+          break
         end
       end
     end
 
-    def s_rule(monthly_shipments)
-      monthly_shipments.each do |month|
-        month.each do |shipment|
-          shipment.discount += shipment.price - lowest_s_price
-        end
+    def s_rule(month)
+      month.each do |shipment|
+        shipment.discount += shipment.price - lowest_s_price
       end
     end
   end
diff --git a/lib/planet_express_express/shipment_reader.rb b/lib/planet_express_express/shipment_reader.rb
index 61e46c6..f04d583 100644
--- a/lib/planet_express_express/shipment_reader.rb
+++ b/lib/planet_express_express/shipment_reader.rb
@@ -30,28 +30,25 @@ module PlanetExpressExpress
         shipment = parse(line)
 
         if shipment.date.year != current_year || shipment.date.month != current_month
-          close_month(shipments)
+          yield shipments
+          shipments.each do |_,v|
+            v.clear
+          end
         end
-        shipments[shipment.size].last.push(shipment)
-        shipments[:all].last.push(shipment)
+        shipments[shipment.size].push(shipment)
+        shipments[:all].push(shipment)
 
         current_year = shipment.date.year
         current_month = shipment.date.month
       end
 
-      shipments
+      yield shipments
     end
 
     private
 
     attr_reader :prices
 
-    def close_month(shipments)
-      shipments.keys.each do |key|
-        shipments[key].push([])
-      end
-    end
-
     def parse(line)
       parts = line.split(" ")
 
diff --git a/spec/planet_express_express_spec.rb b/spec/planet_express_express_spec.rb
index 88cc8d9..181c6ef 100644
--- a/spec/planet_express_express_spec.rb
+++ b/spec/planet_express_express_spec.rb
@@ -7,13 +7,13 @@ RSpec.describe PlanetExpressExpress do
       "r"
     )
 
-    shipments = PlanetExpressExpress::ShipmentReader.new(PlanetExpressExpress::PRICE_LIST).read_shipments(input_file)
-    PlanetExpressExpress::Rules.new(PlanetExpressExpress::PRICE_LIST).apply_rules(shipments)
-    PlanetExpressExpress::DiscountBudget.new(PlanetExpressExpress::DISCOUNT_LIMIT).limit_discounts(shipments)
-
     output = StringIO.new
 
-    PlanetExpressExpress::Formatter.new(output).format(shipments)
+    PlanetExpressExpress::ShipmentReader.new(PlanetExpressExpress::PRICE_LIST).read_shipments(input_file) do |shipments|
+      PlanetExpressExpress::Rules.new(PlanetExpressExpress::PRICE_LIST).apply_rules(shipments)
+      PlanetExpressExpress::DiscountBudget.new(PlanetExpressExpress::DISCOUNT_LIMIT).limit_discounts(shipments)
+      PlanetExpressExpress::Formatter.new(output).format(shipments)
+    end
 
     expected_output = File.read(
       File.expand_path("../fixtures/output.txt", __FILE__)