Prove that R is commutative if and only if R' is commutative.
I'm going to take a wild guess. Let $\displaystyle R$ be a commutative ring and $\displaystyle \phi:R\to R'$ an epimorphism. Then, $\displaystyle R'$ is commutative. To see this let $\displaystyle \phi(r),\phi(s)\in R'$ then $\displaystyle \phi(r)\phi(s)=\phi(rs)=\phi(sr)=\phi(s)\phi(r)$