2. For each language given below, give a context free grammar (CFG) for that language (e.g., a language A, ababbba has a CFG G, that is,

S CDa | CD

C aD

D Sb | b

a) {aⁿ b^n+m a^m | m, n >= 0}

b) {aⁿ bⁿ a^m b^m | m,n >= 0}