The Internal Revenue Service reported the average refund in 2017 was $2,878 with a standard deviation of $520. Assume the amount refunded is normally distributed. a. What percent of the refunds are more than $3,500?
b. What percent of the refunds are more than $3,500 but less than $4,000? (Round intermediate calculations to 2 decimal places and final answer to 2 decimal places.)
c. What percent of the refunds are more than $2,400 but less than $4,000? (Round intermediate calculations to 2 decimal places and final answer to 2 decimal places.)