A review of the service call records of Paul’s Plumbing indicates that the time taken for a service call can be represented by a normal distribution with mean 50 minutes and standard deviation 10 minutes.
a. What is the probability that a service call takes more than 30 minutes? (Be sure to indicate the relevant Z-score for the problem).
b. What is the probability that a service call takes less than an hour? (Be sure to indicate the relevant Z-score for the problem).
c. A plumber is scheduled to make 3 calls in a morning. The times taken for each call are independent of one another. What is the probability that all 3 of the calls will take more than one hour?