6.7 In a recent year, about two-thirds of US. households purchased ground coffee. Consider the annual ground cof-
fee expenditures for households purchasing ground coffee,
assuming that these expenditures are approximately dis-
tributed as a normal random variable with a mean of
$45.16 and a standard deviation of $10.00.
a. Find the probability that a household spent less than $ 25.00
b. Find the probability that a household spent more than
$50.00
c. What proportion of the households spent between
$30.00 and $40.00?
d. 99% of the households spent less than what amount?