Incorrect Answer.
Incorrect Answer.
(p 
r) is an implication, so it can only evaluate to F if its premise r evaluates to T and its
conclusion (p r evaluates to F. But if p is assigned T, then the conclusion
does evaluate to F since r computes to F.
Therefore, any valuation that assigns T to r is a witness to the fact that the
formula r (p r) is not
a tautology.