2. (This exercise is a variation of Exercise 4.5 in Chapter 4 of the textbook) Consider the set of formulas

S = { p, p ? ((q ? r) ? (q ? r)), p ? ((s ? t) ? (s ? t)), s ? q, r ? t, t ? s }

(a) Transform S into a set of formulas in CNF, S'

(b) Transform S' into a set of formulas in clausal form, S''

Assignment Questions 1. Let p, q, r, and s be propositional variables. Which of the following expressions would not be formulas in conjunctive normal form? Why? (a) pVpVp (b) pAqAr (e) p^q?p (g) s (h) -(pVq vr) (i) -p v q V