$($a$)$ Sketch the polymerization of polytetrafluoroethylene. $($b$)$ Calculate the reaction energy $($per mole$)$ for this polymerization. $($c$)$ Calculate the molecular weight of a molecule with $n=500.$

$2\mathrm{.}39$ Repeat Problem $2\mathrm{.}38$ for polyvinylidene fluoride, an ingredient in various commercial fluoroplastics, that has the monomer