Customers arrive at the rate of twenty per hour and the present serving arrangements can cope with thirty per hour for an eight-hour day.

Using the queuing formulae provided, you are required to calculate and state:

(a) the average time in the queue;

(b) the implied value of customers' time if the owner of the service has considered but rejected a faster service arrangement which would cost an extra Rs 20 for an eight-hour day and would raise the service rate to forty per hour.