1.(Exercise 4.4 in Chapter 4 of the textbook) Given the set of clauses {pqr, pr, qr, r} , construct two refutations (i.e. demonstrate using the resolution procedure that the set of clauses is unsatisfiable):

(a)one by resolving the literals in the order {p, q, r}

(b)and the other in the order {r, q, p}