17.7-4. Marsha operates an expresso stand. Customers arrive ac-cording to a Poisson process at a mean rate of 25 per hour. The time needed by Marsha to serve a customer has an exponential distribution with a mean of 90 seconds. (a) Use the M/G/I model to find L,Lq, W, and Wq. (b) Suppose Marsha is replaced by an expresso vending machine that requires exactly 90 seconds for each customer to operate. Find L, Lq , W, and W4. (c) What is the ratio of L, in part (b) to Lq in part (a)? T (d) Use trial and error with the Excel template for the M/G/l model to see approximately how much Marsha would need to reduce her expected service time to achieve the same Lq 17.7-4. Marsha operates an expresso stand. Customers arrive ac-cording to a Poisson process at a mean rate of 25 per hour. The time needed by Marsha to serve a customer has an exponential distribution with a mean of 90 seconds. (a) Use the M/G/I model to find L,Lq, W, and Wq. (b) Suppose Marsha is replaced by an expresso vending machine that requires exactly 90 seconds for each customer to operate. Find L, Lq , W, and W4. (c) What is the ratio of L, in part (b) to Lq in part (a)? T (d) Use trial and error with the Excel template for the M/G/l model to see approximately how much Marsha would need to reduce her expected service time to achieve the same L