[Big-Daddy]

Can someone help me answer the attached question?

Rate is being defined as d[P]/dt, and d[P]/dt = k₃[ES]. So the main challenge is expressing [ES]. I applied the steady-state approximation to find [ES] = [E][S]k₁+k_-2[ES₂] / (k₃+k_-1+k₂[S]). Then I used a mass balance for E, which the presence of [E]₀ implies is necessary. But I can't seem to eliminate all of the extra variables doing that alone. What should I do?