76. Refer to the Buena School District bus data.

a. Refer to the maintenance cost variable. The mean maintenance cost for last year is $450.29, with a standard deviation of $53.69. Estimate the number of buses with a cost of more than $500. Compare that with the actual number.

b. Refer to the variable on the number of miles driven. The mean is 830.11 and the standard deviation is 42.19 miles. Estimate the number of buses traveling more than 900 miles. Compare that number with the actual value.