On Black Friday, customers arrive at a Gap store at a rate of 100 customers per hour during 6am to 12pm. The store is only able to serve 90 customers per hour. Assume that no more customers are coming after 12pm.

 
a). At 9am, how many customers are waiting? Show your work below:

b). How long does it take to serve the 10th customer in the line? Show your work below:

c). If a customer arrives at 9am, how long does it take for her to receive service? Show your work below:

d). What is the average time to serve a customer? Show your work below:

e). When can the store finish serving all the customers?