Determine if the following are tautologies contradiction or

Determine if the following are tautologies, contradiction or contingencies. You cannot use truth tables to justify your answers. Use either logical equivalences or some other means that does not use truth tables. (p^-q) doubleheadarrow (p rightarrow q) -(-(-a -b) rightarrow (z rightarrow (a b))) (-z -y) rightarrow -((z x (-x y))

first statemant was taurologies because both are different statamants

b) and c) i dont know