Solution
= Solution
After the first of two equal-rate clocks <rings>, the residual lifetime of the other clock is, by memorylessness, a fresh exponential variable of rate $\lambda$, independent of the first ringing time and of which clock rang. Hence
$$
V\sim\operatorname{Exp}(2\lambda),
\qquad W-V\sim\operatorname{Exp}(\lambda),
$$
and these variables are independent.