问题204: Construct a truth table for A Determine whether the expression A is a tautology, contradiction or contingency.

Let A≡(p ^ ~r)←→~q.
(a) Construct a truth table for A Determine whether the expression A is a tautology,
contradiction or contingency.
(b) Based on the truth table in part (a), write the Principal Disjunctive Normal Form
(PDNF) and Principal Conjuctive Normal Form (PCNF) of A and ~A