Because of the relatively high interest rates, most consumers attempt to pay off their credit card bills promptly. However, this is not always possible. An analysis
of the amount of interest paid monthly by a bank's Visa cardholders reveals that
the amount is normally distributed with a mean of 28 dollars and a standard
deviation of 9 dollars.
A. What proportion of the bank's Visa cardholders pay more than 30 dollars in
interest?
Proportion =