Do I do it right for the question? And how to find total cost in part B?

A chemical plant stores spare parts for maintenance in a large warehouse. Throughout the working day, maintenance personnel go to the warehouse to pick up supplies needed for their jobs. The warehouse receives a request for supplies, on average, every 2 minutes (Poisson distributed). The average request requires 1.7 minutes to fill (exponential service times). Maintenance employees are paid $20 per hour, and warehouse employees are paid $12 per hour. The warehouse is open 8 hours each day.

1. What is the optimal number of warehouse employees to hire? (Hint: Time spent by maintenance workers waiting in line for supplies should be considered an expense.)

Pn₌₂ = (/)^k x (1- /)

= (0.4/0.5)² x 0.2

= 0.64 x 0.2

= 0.128

2. What is the total cost per hour (waiting plus warehouse employee labour cost) of your solution?

Po = 1/{(1+ / + x ( /)^2 x (m / m - )}

= 1 /{ 1 + 0.8 + x 0.8^2 x (2x5/ 2x5 4)

= 1/ (7/3)

= 0.4286