Istanbul Industries Uses a Kanban System to Manage Production of the MI6

Multiple Choice

Istanbul Industries uses a kanban system to manage production of the MI6 subassembly. In an 8-hour day, they use 100 units per hour and use containers that can hold 23 units each. It takes 120 minutes to fill and move a container of parts to the right place on the MI6 line that is currently rated at a 15% safety factor.
-If the number of containers is reduced by 1, what would be the new required round-trip time, all else being constant?

A) 90 minutes
B) 1 hour
C) 1.8 hours
D) 2 hours
E) Need additional information to compute the value