dotnet__skills/tests/dotnet/csharp-refactoring/golden-patches/extract-subtotal.patch

diff --git a/src/Billing/OrderProcessor.cs b/src/Billing/OrderProcessor.cs
index 449ef77..84199df 100644
--- a/src/Billing/OrderProcessor.cs
+++ b/src/Billing/OrderProcessor.cs
@@ -10,11 +10,7 @@ internal sealed class OrderProcessor
 {
     public Invoice DoStuff(IReadOnlyList<OrderLine> lines, string tier)
     {
-        decimal subtotal = 0m;
-        foreach (var line in lines)
-        {
-            subtotal += line.UnitPrice * line.Quantity;
-        }
+        decimal subtotal = CalculateSubtotal(lines);
 
         decimal shipping = subtotal >= 100m ? 0m : 9.99m;
 
@@ -33,4 +29,15 @@ internal sealed class OrderProcessor
             Math.Round(quoteWithTax, 2),
             shipping);
     }
+
+    private static decimal CalculateSubtotal(IReadOnlyList<OrderLine> lines)
+    {
+        decimal subtotal = 0m;
+        foreach (var line in lines)
+        {
+            subtotal += line.UnitPrice * line.Quantity;
+        }
+
+        return subtotal;
+    }
 }