The Webster National Bank is reviewing its service charges and interest-paying policies on checking accounts. The average daily balance on personal checking accounts is $550, with a standard deviation of $150. In addition, the average daily balances are normally distributed.

a. What percentage of personal checking account customers carry average daily balances in excess of $800?

b. What percentage carry average daily balances below $200?

c. What percentage carry average daily balances between $300 and $700?

d. The bank is considering paying interest to customers carrying average daily balances in excess of a certain amount. If the bank does not want to pay interest to more than 5% of its customers, what is the minimum average daily balance it should be willing to pay interest on?