(a) The duration of phone calls to a Calling Centre is normally distributed with a mean of seven minutes and a standard deviation of two minutes. Calculate the probability that a phone call to the Calling Centre last for between 5 to 10 minutes.
(b) A recent survey found that 56% of mobile phone users, between the ages of 18 to 34, had a smartphone. Suppose a random sample of 100 mobile phone users were selected. What is the probability that less than 50 of them have a smartphone?