Janson's Department Store in Stark, Ohio, maintains a successful catalog sales department in which a clerk 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 averge of 4.0 minutes. Calls tend to follow a Poisson distribution, and service times tend to be exponential.

The Cost of the clerk is $8 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.

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