Aircon, a South African company, services home air conditioners. It is known that times for service calls follow a normal distribution with mean of 50 minutes and a standard deviation of 12 minutes.
a. What is the probability that a single service call takes more than 56 minutes? 

b. What is the probability that a single service call takes between 40 and 60 minutes?
c. The probability is 0.05 that a single service call takes more than how many minutes?
d. Find the shortest range of times that includes 40% of all service calls.
e. A random sample of five service calls is taken. What is the probability that exactly three of them take more than 56 minutes?