HELP PLEASE

19. [-/0.4 Points] DETAILS CUSTOMLARLINALG8 2.1.029. Let A and B be matrices with the following sizes. A: 2 x 1 B: 2 x 1 If defined, determine the size of the matrix A + B. (If an answer is undefined, enter UNDEFINED.) If not defined, explain why. O A + B is defined. O A + B is not defined because A and B have different sizes. O A + B is not defined because A and B have the same size. O A + B is not defined because the number of columns of A does not equal the number of rows of B. O A + B is not defined because the number of rows of A does not equal the number of columns of B