Jamila counts the number of books she has in her locker. She has three times the sum of Carl's and Rachel's books. Carl has c books and Rachel has r books. Which expression could be used to correctly calculate the number of books Jamila has?

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?