The polymer sample has the following composition.

$\backslash$table$[[$Degree of polymerization,$2000,3000,4000,5000],[\%$ of composition,$10,20,30,40]]$

If the number average molecular weight of the sample is $112000,$ name the monomer $($contains carbon and hydrogen only$)$ and its functionality. Calculate the polydispersity index of the polymer sample.