Consider the polysterification reaction occurring between molecules $\frac{C}{O}OH-A-\frac{C}{O}OH,OH-$

$B-OH$ in an equimolar mixture with an initial concentration of $0\mathrm{.}252mo\frac{l}{k}g.$ This reaction

occurs in two stages. In the first stage of pre$-$polymerization, the monomer is taken to a

conversion of $81\mathrm{.}3\%$ at $90C,$ this process takes $3$ hours. In the second stage, the

polymerization occurs at a temperature of $145C,$ yielding the following data:

a$)$ Calculate the kinetic constant for this process at $145C.$

b$)$ If the activation energy is of $47\mathrm{.}8k\frac{J}{m}ol,$ how much time would it take to reach an extent

of reaction of $90\%$ at $130C$ and at $160C$ with the same initial concentration as in a$).$