and thus K M2 /V 2 is a reasonable asymptotic approximation to t * s2 . Note that the underlying assumption in the analysis is that t c1 t * s2 . Since it does not make much sense to ask how long it takes for the right hand side of (64) to accumulate to s * 2 , we have to rely on an approximation method to find a matching timescale. To do this, we ask how long it takes for s 2 to accumulate to s * 2 (1-ν), where ν is an appropriate small parameter (i.e., ν 1). A natural choice for ν is K M2 /(V 2 • t s1 ), and it follows that a reasonable estimate on the time it takes s 2 to reach s * 2 is give by t * * s2 :