Matrix A ha s m rows and n+ 5 columns; matrix B has m rows and `11 - n` columns. If both AB and BA exist, then (A) AB and BA are square matrix (B) AB and BA are of order `8 xx 8` and `3 xx 13`, respectively (C) `AB=BA` (D) None of these

Explanation

If both AB and BA exist, then the number of columns of A is equal to the number of rows of B. Therefore,
`n+5=m` (1)
And the number of columns of B is equal to the number of rows of A. therefore,
`11-n=m` (2)
Solving (1) and (20, we get `n=3` and `m=8`. Hence, A has order `8xx8` has order `8xx8`. Hence, both AB and BA are square matrices.