5.35 A company services copiers. A review of its records shows that the time taken for a service call can be represented by a normal random variable with a mean of 75 minutes and a standard deviation of 20 minutes. a. What proportion of service calls takes less than 1 hour? b. What proportion of service calls takes more than 90 minutes? c. Sketch a graph to show why the answers to parts (a) and (b) are the same. d. The probability is 0.1 that a service call takes more than how many minutes