The Malthouse Charity Run is a 5 kilometre race. The time taken for each runner to complete the race was recorded. The data was found to be normally distributed with a mean time of 28 minutes and a standard deviation of 5 minutes.
A runner who completed the race is chosen at random.
Write down the probability that the runner completed the race in more than 28 minutes.
3b. [2 marks]
Calculate the probability that the runner completed the race in less than 26 minutes.
3c. [3 marks]
It is known that 20% of the runners took more than 28 minutes and less than minutes to complete the race.
Find the value of .