You want to determine the number of docks required for a receiving and shipping facility. The costs of operating a truck are $ 35.00 per hour and the cost of operating a dock is $ 50 per hour. 2 trucks arrive at this warehouse per hour and 1.5 trucks leave per hour. A truck is loaded is .6 hour and the time to unload is .7 hour. 

a. If receipt and shipping docks are not going to be shared, what is the minimum number of entry docks needed for the system to reach steady state? 

b. What is the optimal number of inlet springs? 

c. If the receiving and shipping docks are not to be shared, what is the minimum number of departure docks needed for the system to reach steady state? 

d.What is the optimum number of output springs?