estion 33. Consider the following block matrices
$X = \begin{bmatrix} I & A \\ B & I \end{bmatrix}$, $Y = \begin{bmatrix} C \\ D \end{bmatrix}$,
where A is an $m \times n$ matrix and I denotes the identity matrices with appropriate
sizes. Suppose that we can do the product XY. How many rows do C and D have?
(a) There is no conclusion from the given information, we must know the size of B.
(b) Both C and D have m rows.
(c) Both C and D have n rows.
(d) C has m rows and D has n rows.
(e) C has n rows and D has m rows.