posted by Johnny .
Bank XYZ is hiring, and they would like to determine the number of tellers they should hire. Each teller is paid $15 per hour. Bank XYZ has assessed a cost on customer waiting at $10 per customer in line per hour. (In other words, each customer standing in line at the bank and not being helped by a teller costs the bank $10 per hour.) How many tellers must the Bank hire to minimize their total hourly cost? Assume customers arrive according to a Poisson process at rate 20 per hour, and that each customer spends an exponentially distributed amount of time with a teller that has mean 8 minutes.
I believe my p=8 min/cust and my a=3 min/cust. However, I am getting a negative number when coming up with my Tq. I need some help.