I am having trouble trying to solve the questions using excel solver

1. The reference desk at a library receives requests for assistance. Assume that a Poisson probability distribution with a mean rate of 10 requests per hour can be used to describe the arrival pattern and that service times follow the exponential probability distribution with a mean service rate of 12 requests per hour.

a. What is the probability of no requests for assistance in the system?

b. What is the average number of requests that will be waiting for service?

c. What is the average waiting time in minutes before service begins?

d. What is the average time at the reference desk in minutes (waiting time plus service time)? e. What is the probability that a new arrival has to wait for service?

2. ABC Design provides decorating assistance to its customers. In normal operations, an average of 2.5 customers arrive each hour. One design consultant is available to answer questions and make product recommendation. The consultant averages 10 minutes with each customer.

a. Compute the operating characteristics of the customer waiting line, assuming Poisson arrivals and exponential service times.

b. Service goals dictate that an arriving customer should not wait for service more than an average of 5 minutes. Is this goal being met? If not, what action do you recommend?

c. If the consultant can reduce the average time spent per customer to 8 minutes, what is the mean service rate? Will the service goal be met?