The Sizes of Two Matrices Are Given $\mathrm { A }$

Multiple Choice

The sizes of two matrices are given. Find the size of the product AB and the size of the product BA, if the given product
can be calculated.
- $\mathrm { A }$ is $2 \times 1 ; \mathrm { B }$ is $1 \times 1$ .

A) $\mathrm { AB }$ is $1 \times 2 ; \mathrm { BA }$ is $1 \times 1$ .
B) AB cannot be calculated; $B A$ is $1 \times 2$ .
C) $\mathrm { AB }$ is $2 \times 1$ ; BA cannot be calculated.
D) $\mathrm { AB }$ is $2 \times 2 ; \mathrm { BA }$ is $1 \times 1$ .