Berlin Industries Uses a Kanban System to Manage Production of the R-15

Multiple Choice

Berlin Industries uses a kanban system to manage production of the R-15 subassembly. They have an hourly demand for 250 units and use containers that can hold 50 parts each. It takes 90 minutes to fill and move a container of parts to the right place on the R-15 line that is currently rated at a 20% safety factor.
-How many containers should the kanban system of Berlin Industries be using?

A) 540
B) 100
C) 50
D) 9
E) 1.5