The Sizes of Two Matrices Are Given $4 \times 1$ ; B Is

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

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