A machine has two components. One component is at work. The 2nd component sits idle but is activated after first one has failed. The machine fails only after both components have failed. Let X and Y represent each component's time till failure. Let Z represent machine's time till failure. Let Mx(t)=1/(1-t) and My(t)=1/(1-2t), find E(Z), Var(Z), E(Z^3)