Hi!

I can not solve this exercise.I need help

Let A be any commutative ring with identity 1 $\displaystyle \neq{}$ 0 .Let R be the set of all group homomorphism of the additive group A to itself with addition defined as pointwise addition of functions and multiplication defined as function composition.Prove that these operations make R into a ring with identity .Prove that the units of R are the group automorphism of A