1) In a certain company, the amount being spent on personal phone calls followed a normal distribution with a mean of $500 per month and a standard deviation of $50 per month. What is the probability that a randomly selected month had a phone bill: (a) Between $375 and $520? Round final answer to four decimal places. (b) Greater than $530? Round final answer to four decimal places. (c) Less than $390? Round final answer to four decimal places. (d) More than $500? Round final answer to four decimal places.

2. According to flightstats.com, American Airlines flights from Dallas to Chicago are on time 80% of the time. Suppose 15 flights are randomly selected, and the number of on-time flights is recorded. Round all answers to four decimal places. Treating this as a binomial distribution: (a) What is the probability that exactly 10 flights are on time? (b) What is the probability that fewer than 10 flights are on time? (c) What is the probability that at least 10 flights are on time? (d) What is the probability that between 8 and 10 flights, inclusive, are on time?

3. Suppose a simple random sample of size =65 is obtained from a population with a mean of 57 and a standard deviation of 12. (a) What is the mean of the sampling distribution? In other words, what is the mean of the 's, i.e. find . (b) What is the standard deviation of the sampling distribution? Find . (c) What is ( >60)? Round final answer to four decimal places. (d) What is ( <52)? Round final answer to four decimal places. (e) What is (54< <62)? Round final answer to four decimal places.