Answer
($i$) and ($ii$)
Work Step by Step
(i)
For a sum of matrices, they must have the same dimension.
A has the same dimension as ... A, so this operation is always possible.
(ii)
The scalar product cA is the $m\times n$ matrix obtained by multiplying each entry of $A$ by $c$.
A can have any dimension, so this is also always possible.
(iii)
For a matrix product,
the second matrix must have as many rows as the first has columns.
$A\cdot A$ is only possible for square matrices.
(Not possible for any dimension)
