An analysis of the amount of interest paid by ABX banks' visa card holders reveals that the amount is normally distributed with a mean of $27 and a standard deviation of $7.

a. What proportion of the Bank's Visa card holders pay more than $30 in interest? (2.5 marks)

b. What proportion of the Bank's Visa card holders pay more than $40 in interest? (2.5 marks)

c. What proportion of the Bank's Visa card holders pay less than $15 in interest? (2.5 marks)

d. What interest payment is exceeded by only 20% of the bank's Visa cardholders? (2.5 marks)