A mechanic is able to install a new muffler every 20 minutes (3 per hour) according to a negative exponential distribution. Customers seeking this service arrive at the shop on an average of 2 per hour, following a Poisson distribution. They are served on a first-in, first-out, basis and come from a very large almost infinite population of buyers. It is estimated by a manager that waiting time in terms of customer dissatisfaction and lost goodwill is 15 dollars per hour waiting in line. The mechanic is paid 11 dollars per hour and works 8 hours a day. The shop is going to buy new equipment that costs 10,000 and will increase its service rate to 6 cars per hour. How much is this going to cost in customer dissatisfaction per day and how many days until the equipment pays for itself? (given that customer dissatisfaction before this cost 160 per day)

a. 20 per day, 104 days

b. 160 per day, 72 days

c. 20 per day, 72 days

d. 160 per day, 104 days.