Matrix addition and subtraction are trivial. State truw false for the following: 1. Matrix multiplication is commutative meaning AB= BA 2. If the product AB exists, then BA will exist as well. 3. The transpose of a matrix is the inverse of the matrix. 4. (AB)^t = A^t B^t ( where t stands for the transpose) 5. What about (A+B)^t.

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?