Compute the product using the methods below. If a product is undefined, explain why. 5 2 a. The definition where Ax is the linear combination of the columns of A using the corresponding entries in x as 4 weights. -2 - 3 5 b. The row-vector rule for computing Ax. 6 4 b. Set up the product Ax using the row-vector rule. Select the correct choice below and, if necessary, fill in the answer boxes to complete your choice. O A. (Do not simplify.) O B. (Do not simplify.) O C. The matrix-vector Ax is not defined because the row-vector rule states that the number of columns in matrix A must match the number of entries in the vector x