In a memo to all those involved in tax preparation, the IRS indicated that the mean amount of refund was $1,600 with a standard deviation of $850. Assume the distribution of the amounts returned follows the normal distribution.
a. What percent of the refunds were between $1,600 and $2,000?
b. What percent of the refunds were between $900 and $2,000?
c. According to the above information, what percent of the refunds were less than $0. That is, the taxpayer owed the IRS.