Given covering space actions of groups G1 on X1 and G2 on X2, show that the action of G1×G2 on X1×X2 defined by (g1,g2)(x1,x2)=(g1(x1),g2(x2)) is a covering space action, and that (X1×X2)/(G1×G2) is homeomorphic to X1/G1×X2/G2.