What is the product? 3 times the 1 by 4 matrix, row 1, column 1, 1 column 2, negative 4 column 3, 5 column 4, negative 7

Multiply each entry of the row matrix by 3: 3(1) = 3, 3(−4) = −12, 3(5) = 15, and 3(−7) = −21. The resulting matrix is [3, −12, 15, −21], which is choice C.

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