4. Consider the following identities for regular expressions; some are false and some are true. You are asked to decide which and in case it is false to provide the correct counterexample. (a) R(S+T)=RS+RT (d) (R+S)"=R"+5* (e) S(RS+S)*R-RR*S(RR*S)* (f) (RS+R)*R-R(SR+R)* a) (d) is false and a counterexample is b) (d) is true c) (d) is false and a counterexample is d) (c) is false and a counterexample is