The minute a stop market has one pump for gasoline,  which can service 10 customers per hour(poison distributed). Cars arrive at the pump at a rate of 5 per hour (poisson distributed).

Determine; 

a. The average queue length _ customer 

b. The average time a car is in the system _ minutes 

c. The average time a car must wait before being served_ minutes 

d. The probability that exactly one car will be in the system is _