Show the formula in Excel to solve the equation.

Suppose that the waiting time for a license plate renewal at a local office of a state motor vehicle department has been found to benormally distributedwith a mean of 28 minutes and a standard deviation of 7 minutes. Suppose that in an effort to provide better service to the public, the director of the local office is permitted to provide discounts to those individuals whose waiting time exceeds a predetermined time. The director decides that 15 percent of the customers should receive this discount. What number of minutes do they need to wait to receive the discount?