For a whole life insurance payable at the moment of death, you are given that E[Z] = 0.25. Assume that the forces of interest and mortality are constant. Calculate Var(Z).

So I know Ax = E[Z] = mu / (mu + d) when mu(x) = mu and we're supposed to use this result to help us calculate this problem. But I'm not sure how that fits together. Does anyone know how to use this or any other way to find the Var(Z)?

Thank you!