A recent report indicated a typical family of four spends $490 per month on food. Assume the distribution of food expenditures for a family of four follows the normal distribution, with a standard deviation of $90 per month.
a. What percent of the families spend more than $30 but less than $490 per month on food?
b. What percent of the families spend less than $430 per month on food?
c. What percent spend between $430 and $600 per month on food?
d. What percent spend between $500 and $600 per month on food?