Q6. Here are some techniques for showing implications are universally true. In each case the conclusion is that PQ is universally true. Show that each technique works. (a) It is sufficient to show that Q is universally true. (b) Unsatisfiable precondition. It is sufficient to show that P is unsatisfiable 1 (c) Subsetting the precondition: If P is of the form P0P1Pn, it is sufficient to show that PQ is universally true, where P is the conjunction of some subset of the conjuncts of P. For example it is sufficient to show P0Q is universally true or that P0PnQ is universally true