Sulphur trioxide is prepared by the following two reactions:

$\begin{array}{c}{\mathrm{S}}_8\left(\mathrm{s}\right)+8{\mathrm{O}}_2\left(\mathrm{g}\right)⟶8{\mathrm{SO}}_2\left(\mathrm{g}\right)\\ 2{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)⟶2{\mathrm{SO}}_3\left(\mathrm{g}\right)\end{array}$

How many grams of ${\mathrm{SO}}_3$ are produced from 1 mol of ${\mathrm{S}}_8$?