In a recent year, about two-thirds of U. S. households purchased ground coffee. Consider the annual ground coffee expenditures for households purchasing ground coffee, assuming that these expenditures are approximately distributed as normal random variable with a mean of $45.16 and a standard deviation of $10.00. a) What proportion of the households spent between $31.00 and $48.00 b) 72.91% of the households spent less than what amount?