The daughter of the owner of a local hamburger restaurant is preparing to open a new fast-food restaurant called Hasty Burgers. Based on the arrival rates at her father's outlets, she expects customers to arrive at the drive-up window according to a Poison distribution, with a mean of 25 customers per hour. The service rate is flexible; however, the service times are expected to follow an exponential distribution. The drive-in window is a single-server operation. What service rate is needed to keep the average number of customers in the service system (waiting line and being served) to five? mu = customers per hour. (Enter your response as an integer.)