which of the following maps are homomorphisms? if the map is a homomorphism, what is the kernel? (a) phi : R* maps to GL2(R) defined byphi(a)= (1 00 a)(b) phi :R maps to GL2(R) defined by phi(a)= (1 0a 1)(c) phi :GL2(R) maps to R defined by phi ((a c d)) = a+d(d) phi : GL2(R) maps to R* defined by phi ((a b c d)) = ad-bc(e) Phi: M2(R) maps to R defined by phi ((a b c d)) = b,