Find context-free grammars for the following languages (with n ? 0, m ? 0, k ? 0).

(a) L = {w ?{a,b}? : na(w) = nb(w) + 2}

(b) L = {aⁿb^mc^k : n = m or m =/ k}

(c) L = {a_nb^mc^k : k = n + m}

(d) L = {aⁿb^mc^k : k =| n?m |}

(e) L = {aⁿb^mc^k : k =/ n + m}