Costing

“It has been agreed to pay time a half to sales assistants that work on Sundays. The normal hourly rate is $20 per hour. In total five sales assistants will be needed for the six hours that the store will be open on Sunday. They will be able to take a half day off (four hours) during the week. Staffing level will be allowed to reduce slightly during the week to avoid extra cost being incurred.”

There is no other information regarding staffing costs in the question. In the answers they have calculated the increment staffing costs for 50 sundays as : 5 x 6 x 50 x 1.5 x 20 = $45,000. I get this part, but when they are given four hours off during the week, should we not reduce the staffing costs by: 5 x4 x 20 x 50 = $20,000? This wasn’t the case in answers.