Been working for hours on my homework...brain is fried. Can not figure out this last problem. Any help/guidance would be appreciated. Thanks.

Prove or disprove that if $\displaystyle phi$ and $\displaystyle psi$ are homomorphisms between groups G and G', then the set

H = { x element of G | $\displaystyle psi$(x) = $\displaystyle phi$(x)}

is a subgroup of G.

thanks again!