The water level in a vat changed by −9.9 inches in 2.25 hours as the vat was drained. What is the average change in the vat's water level per hour? Enter the your answer in the box as a decimal.

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?