Use the calculator for these calculations. Round your answer to the nearest thousandth, if necessary: 18x(27+36/3) (21+36/74-18x3)x10 square root of 3/2 square root of 281^2-160^2 2^10-2^9 square root of 8x square root of 9-7

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?