Please answer the question (b) step by step and include the clear explanation.

Question 4 Multi-Server Queue A supermarket manager is trying to decide how many cashers to employ for the peak time. The service times for check outs are exponentially distributed with a mean service time of 3 minutes. Customer arrivals to cashiers follow a Poisson arrival process with an average 110 customers per hour. a. What is the minimum number of cashers that would be needed to have the utilization less than one? b. If the waiting time is too long, customers might leave the store or even do not enter the store. It is estimated that for every minute of waiting time, the supermarket loses a potential profit of 50HKD every hour from lost sales. The hourly wage for a casher is 80HKD/ hour. How many cashers should the supermarket employ to maximize its profit? (Keep four decimal places.)