General Hospital's patient account division has compiled data on the age of accounts receivable. The data collected indicate that the age of the accounts follows a normal distribution with a mean age of 28 days and a standard deviation of 8 days.

(a) What portion of the accounts is between 20 and 40 days old

(b) The hospital administrator is interested in sending reminder letters to the oldest 15% of accounts. How many days old should an account be before a reminder letter is sent?

(c) The hospital adminstrator wants to give a discount to those accounts that pay their balance by the twenty-first day. What percentage of the accounts will receive the discou