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. What is the maximum inventory of heating elements in the system? a. 1,680 b. 540 c. 240 d. 900