Use the pumping lemma to prove that thse languages are not context free:

a. {0ⁿ1ⁿ0ⁿ1ⁿ|n >= 0}

b. {t₁#t₂#...t_k#|k >= 2, each t_i {a,b}*, and t_i = t_j for some i =/= j}