The Sizes of Two Matrices a and B Are Given $A$

Multiple Choice

The sizes of two matrices A and B are given. Find the sizes of the product AB and the product BA, if the products are
defined.
- $A$ is $1 \times 4 , B$ is $4 \times 1$ .

A) $\mathrm { AB }$ is undefined, BA is $4 \times 4$ .
B) $\mathrm { AB }$ is $4 \times 4$ , BA is $1 \times 1$ .
C) $\mathrm { AB }$ is $1 \times 1 , \mathrm { BA }$ is undefined.
D) $\mathrm { AB }$ is $1 \times 1$ , $\mathrm { BA }$ is $4 \times 4$ .