Question: During the early morning hours, customers arrive at a branch post office at an average rate of 45 per hour (Poisson), while clerks can handle transactions in an average time (exponential) of 4 minutes each. Find:

i) The average number of customers waiting for service if 6 clerks are used

ii) The minimum number of clerks needed to keep the average time in the system to under 5 minutes

iii) If clerk cost is $30 per hour and customer waiting time represents a "cost" of $20 per hour, how many clerks can be justified on a cost basis?