$*$I am stuck on Part C$*$ Another Answerer said it was $$22\mathrm{.}50$ but it came back incorrect. Janson's Department Store in Stark, Ohio, maintains a successful catalog sales department in which a clerk takes orders by telephone. If the clerk is occupied on one line, incoming

phone calls to the catalog department are answered automatically by a recording machine and asked to wait. As soon as the clerk is free, the party who has waited the longest is

transferred and serviced first. Calls come in at a rate of about $12$ per hour. The clerk can take an order in an average of $3\mathrm{.}0$ minutes. Calls tend to follow a Poisson distribution, and

service times tend to be negative exponential.

The cost of the clerk is $$12$ per hour, but because of lost goodwill and sales, Janson's loses about $$30$ per hour of customer time spent waiting for the clerk to take an order.

a$)$ The average time that catalog customers must wait before their calls are transferred to the order clerk $=4\mathrm{.}5$ minutes $($round your response to two decimal places$).$

b$)$ The average number of callers waiting to place an order $=$

callers $($round your response to two decimal places$).$

The present total cost per hour $($service cost $+$ waiting cost$)=$$$,$ per hour $($round your response to two decimal places$).$

c$)$ Janson's is considering adding a second clerk to take calls. The store's cost would be the same $$12$ per hour. The total cost $($service cost $+$ waiting cost$)$ $ per hour $($round

your response to two decimal places$).$