If the language $A=\{a^m{b}^n{c}^n|m,n0\}$ and the language $B=\{a^n{b}^n{c}^m|m,n0\}$ then:

$AB=\{a^n{b}^n{c}^n|n0\},$ is not context free.

$AB=\{a^n{b}^n{c}^n|n0\},$ is context free.

$AB=\{a^m{b}^{mn}{c}^m|m0\},$ is not context free.

$AB=\{a^m{b}^m{c}^m|m0\},$ is context free.