The manager of a branch of a major bank wants to improve service. She is thinking about giving $1 to any customer who waits in line for a period of time that is considered excessive. (The bank ultimately decided that more than 8 minutes is excessive). However, to get a better idea about the level of current service, she undertakes a survey of customers. A student is hired to measure the time spent waiting in line by a random sample of 50 customers. Using a stopwatch, the student determined the amount of time between the time the customer joined the line and the time he or she reached the teller. The times were recorded.

a. Construct a 90% confidence Interval estimate of the mean waiting time for the bank's customers. Interpret your answer.

b. Perform a 1 sample t-test to test the claim that the mean wait time is less than 8 mins. Test at a significance level of 5%.

Please explain how to solve an issue like this in Excel.