ITERATIONAND TS REQUIREMENTS handles several interesting requirements o Support for variations in third-party external services Complex pricing rules o Pluggable business rules o a design to refresh a gui window when the sale total changesITERATION 2 AND ITS REQUIREMENTS handles several interesting requirements ⚫ Support for variations in third-party external services. ⚫ Complex pricing rules. ⚫ Pluggable business rules. ⚫ A design to refresh a GUI window when the sale total changes