Let $$A = \left[\begin{array}{c} -3\cr 1\cr -3 \end{array}\right].$$ If possible, compute the following. If an answer does not exist, enter DNE. If an answer is a $1 \times 1$ matrix, enter a number without any brackets.

$A^T A =$  help (matrices)

$A A^T =$  help (matrices)