If \(A = \left( {\begin{array}{*{20}{c}} 1&2\\ 2&3\\ 3&4 \end{array}} \right)\) and \(B = \left( {\begin{array}{*{20}{c}} 1&2\\ 2&1 \end{array}} \right),\) then which one of the following is correct?
1
Both AB and BA exist
2
Neither AB nor BA exists
3
AB exists but BA does not exist
4
AB does not exist but BA exists