a call center takes four activities in serving a customer. activities a, b, and d are staffed by one employee, and activity c has two employees (for a total of five employees). the processing time for each activity is given as follows: activity processing time per customer wage ($/hour) a 40 seconds 10 b 30 seconds 16 c 2.5 minutes 12 d 1.5 minutes 10 assume demand is unlimited. what is the cost of direct labor in $ per customer?