M_{r,101} = M_{r,100} + \frac{dM_{r}}{dr} |_{100}

Q_{M} ≡ 1 − \frac{M_{r}}{M_{tot}}  ⇒  M_{r} = M_{tot}(1 − Q_{M})

lifetime T ∼ \frac{amount of fuel}{rate of burning fuel} = \frac{M}{L}