The Briggs-Haldane model assumes that very soon the rate of change of [ES] is small in comparison to [E] and [S], so that d[ES]/dt is almost zero. Using this assumption and the differential equation from your answer to Part b of Exercise 3, solve for [ES] in terms of [E][S]. Define K as an appropriate constant, and in a similar fashion to Exercise 3 complete the solution of v = d[P]/dt as k3[E0][S]/(K + [S]), where [E0] is the constant [E] + [ES] (Danby 1997)