Question regarding internal revenue service

Question

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

1. What range of values would account for virtually all (99.73%) of the tax refunds?
2. What percent of the refunds are more than $3,000
3. What percent of the refunds are more than $3,000 but less than $3,500?
4. What percent of the refunds are more than $2,500 but less than $ 3,500?
5. What percent of the refunds are less than $ 3,000?
6. What amount of tax refund will account for 90 percent of the returns?
7. the returns?