Problem $6$: Non$-$Context$-$Free Languages

Show that these languages are not context$-$free:

A$.$The language of palindromes over $\{0,1\}$ containing equal numbers of $0\text{'}$s and $1\text{'}$s$.$

B$.$ The language of strings over $\{1,2,3,4\}$ with equal numbers of $1\text{'}$s and $2\text{'}$s and equal numbers of $3\text{'}$s and $4\text{'}$s$.$