Customers send emails to a help desk of an online retailer every 4 minutes, on average, and this inter-arrival time is exponentially distributed. The online retailer has three employees answering emails. It takes on average 10 minutes to respond to an email and this time also follows exponential distribution. Currently, each of the three employees has an email address that is posted on the website; so a customer will randomly choose one (with equal probability) to write email to. The email goes to that address and will be answered by that employee. Find the following operational measures.

a) Utilization of the three employees

b) Average number of emails sitting in each employee's mailbox waiting to be answered

c) Average waiting time for a customer to receive an answer after he/she sent out the email (the Internet speed is excellent so do not worry about the email online delivery time)

d) Because most of the emails are asking quick questions, the customers usually wait online for answers after sending out the email. So, they would really appreciate a quick response. How would you redesign the email answering system to provide better customer satisfaction? Try to think of the most economic and easy-to-implement way of improvement and justify your answer.