For stoichiometric balanced (e.g., [A]0=[B]0 ) step-growth reaction (e.g., functional group A can only react with function group B), (a) write the kinetic equation for an external acid catalyzed step-growth reaction; (b) solve the kinetic equation of (a) and express the concentration [A] as a function of time and the initial concentration [A]o; (c) write the kinetic equation for a self-catalyzed step-growth reaction; (d) solve the kinetic equation of (c) and express the concentration [A] as a function of time and initial concentration [A]o