Can I have the formula to calculate Average Flow Time, Flow Rate and Inventory.

An urgent care clinic is open from 10am till 6pm. In all 5 patients go through the clinic during those 8hrs of clinic operation. The arrival and exit times of the patients is provided below: Patient A: Arrival 10am exit 10:30am Patient B: Arrival 11 am exit 12pm Patient C: Arrival 11:30am exit 1pm Patient D: Arrival 12:30pm exit 2pm Patient E: Arrival 5pm exit 6pm What is the average Flow Time of patients in the clinic? a) 1.6hrs/ patient b) 0.625 patient /hr c) 1.10hrs/ patient d) 1.89hrs/ patient Average Flow Rate? Average Inventory