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 $1 \times 4$ ; B is $1 \times 4$ .

A) $\mathrm { AB }$ is $1 \times 1 ; \mathrm { BA }$ is $4 \times 4$ .
B) $\mathrm { AB }$ is $4 \times 1 ; \mathrm { BA }$ is $1 \times 4$ .
C) AB cannot be calculated; BA cannot be calculated.
D) $\mathrm { AB }$ is $1 \times 4$ ; $\mathrm { BA }$ is $4 \times 1$ .