Electricity bills: According to a government energy agency, the mean monthly household electricity bill in the United States in 2011 was $ 109.72. Assume the amounts are normally distributed with standard deviation $24.00. Use the TI-84 Plus calculator to answer the following. (a) What proportion of bills are greater than $131? (b) What proportion of bills are between $87 and $140? (c) What is the probability that a randomly selected household had a monthly bill less than $ 125? Round the answers to at least four decimal places