Using number$-$average molecular weight data $($per Table $4\mathrm{.}4$a$),$ it is possible to convert each $x_i$ entry into its corresponding $w_i$ value

using the following equation:

$w_i=\frac{M_i{x}_i}{{\displaystyle \underset{?}{\overset{?}{}}}{M}_i{x}_i}$

$($a$)$ Make this conversion for all of the $x_i$ items in the following table.

$($b$)$ Compute the weight$-$average molecular weight $(\frac{?}{\text{b}\text{a}\text{r}}(M{)}_w)$ for this polymer.

$\frac{?}{\text{b}\text{a}\text{r}}(M{)}_w=i$