* Refactor.

lib/item.rb

@@ -27,11 +27,11 @@ def to_s
 
     private
     def tax_rate
-      @tax_rates.tax_rate_for_good(name)
+      @tax_rates.tax_rate_for_good name
     end
 
     def unit_tax
-      TaxCalculator.calc_tax(unit_price, tax_rate)
+      TaxCalculator.calc_tax unit_price, tax_rate
     end
 
     def unit_total

lib/numeric_money_format.rb

@@ -3,7 +3,7 @@ module NumericMoneyFormat
     def to_formatted_s(format = :default)
       return super() unless format == :money
 
-      sprintf("%.2f", self)
+      sprintf "%.2f", self
     end
   end
 end

lib/receipt.rb

@@ -20,8 +20,8 @@ def to_s
       <<EOF
 #{@goods.join("\n")}
 
-Sales Taxes: #{tax.to_formatted_s(:money)}
-Total: #{total.to_formatted_s(:money)}
+Sales Taxes: #{tax.to_formatted_s :money}
+Total: #{total.to_formatted_s :money}
 EOF
     end
   end

lib/shopping_cart.rb

@@ -16,6 +16,6 @@ def initialize(items)
   end
 
   def receipt
-    Receipt.new(items)
+    Receipt.new items
   end
 end

lib/tax_calculator.rb

@@ -1,7 +1,7 @@
 module TaxCalculator
   def self.calc_tax(amount, tax_rate)
     tax = amount * tax_rate
-    round_up_to_nearest_5_cents(tax)
+    round_up_to_nearest_5_cents tax
   end
 
   def self.round_up_to_nearest_5_cents(amount)