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 five minutes and a processing time of one hour. The container size is 60 heating elements, and the safety factor is 10 percent. How many Kanban cards should be used? a. 6 b. 4 c. 5 d. 3