During an annual heating season, the average gas bill for customers in a New England community heating their homes with gas was $457. Assuming a normal distribution and a standard deviation of $80:
a. What proportion of homes heating with gas had a gas bill over $382?
b. What proportion of homes heating with gas had a gas bill between $497 and $537?
c. What amount was exceeded by only 2.5% of the homes heating with gas?
d. What amount was exceeded by 95% of the homes heating with gas?