A muffler company advertises that you will receive a rebate if it takes longer than 28 minutes to replace your muffler. Experience has shown that the time taken to replace a muffler is approximately normally
distributed with a mean of 25 minutes and a standard deviation of 3 minutes
a) What proportion of customers receive a rebate?
b) What proportion of mufflers take between 19and 25 minutes to replace?
c) What should the rebate-determining time of 28 minutes be changed to if the company wishes to
provide only 2.5% of customers with a rebate?