The finish times for marathon runners during during a race are normally distributed with a mean of 200 minutes and a standard deviation of 60 minutes. 

a) What is the probability that a runner will complete the marathon within 6 hours? 

b) Calculate to the nearest minute, the time by which the first 9% runners have completed the marathon. 

c) What proportion of the runners will complete the marathon between 1 hours and 4 hours?