Cletus and Spike Company is implementing a Kanban system for a heated water bowl manufacturing line that produces 1,500 units in an eight-hour day. The heating element has a waiting time of 30 minutes and a processing time of one hour. The container size is 40 heating elements, and the safety factor is 15 percent. How many Kanban cards should be used? a. 10 b. 11 c. 9 d. 8