4. 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 $850, 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 $1200
the bank should be willing to pay interest on?
b. What percentage carries average daily balance below $300?
c. The bank is considering paying interest to customers carrying average daily balance 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?