Please answer ASAP. Show solutions and formulas on how to get the red blanks. Please explain

Trader Toe's is a popular grocery store which has on average 20 customers arriving every hour, with a standard deviation of interarrival times of 2 minutes. There is one line for checkout and it is currently operated by two employees. Each employee spends on average 4.5 minutes to checkout a customer. The checkout times follow an exponential distribution. a. (6 points) Assume that every customer coming to the store buys something and so must go through the checkout. Then, what is the average wait time that a customer has to wait in line before getting served by the checkout employees? 4.28min b. (4 points) What is the average number of customers who are at the checkout desk, either waiting or currently being served? 2.93 customers. c. (4 points) If there are no customers requiring checkout, the employees are sorting returned items, which there is always plenty of. Suppose that on average it takes 5 mins to sort a single item (record that it has been returned and place it in its position). How many items can the two employees sort over a 12-hour shift? 72 items d. (3 points) As a special service, the store offers free snacks for customers waiting in the checkout line (the customers who are currently served by the checkout employees are already busy with payment so they do not get free snacks.) The store manager estimates that every minute of customer waiting time costs the store 75 cents because of the free snack service. What is the hourly cost for the store due to this service? $64.20