4.3 Represent the following sentences by predicate calculus wffs. (L toward extravagance rather than economy in the number of different predicates and terms used. Do not, for example, use a single predicate letter to represent each sentence.) (a) A computer system is intelligent if it can perform a task which, if performed bya human, requires intelligence. (b) A formula whose main connective is a is equivalent to some formula whose main connective is a V. (c) If the input to the unification algorithm is a set of unifiable expressions, the output is the mgu; if the input is a set of non-unifiable expressions, the output is FAIL (d) If a program cannot be told a fact, then it cannot learn that fact. (e) If a production system is commutative, then, for any database, D, each member of the set of rules applicable to D is also applicable to any database produced by applying an applicable rule to D