Suppose the mean expenditure per customer at a tire store is $80.00, with a standard deviation

of $10.00. If a random sample of 40 customers is taken, what is the probability

a) that the sample average expenditure per customer for this sample will be $87.00 or

less?

b) that the sample average expenditure per customer for this sample will be $87.00 or

more?

c) that the sample average expenditure per customer for this sample will be between

$70.00 and $85.00?