ANSWERS TO LESSON FOUR

       I.   Which formulae are well-formed (W) and which aren't (~W).

           A.   (P -> Q -> R) ; ~W

           B.   (P -> Q) v (R v B) ; W

           C.   [(P -> S) & (F <-> G)] <-> (G & ~Q) ; W

           D.   ((L & F)) ; ~W

           E.   (T v S) ; W

           F.   Z -> [R -> (P v G)] ; W

           G.   v P -> W ; ~W

           H.   ~~~~F ; W

           I.   T -> [(G -> Y) & (F v B) ; ~W

           J.   F ~F & ; ~W