The reaction of 4-methyloct-1-ene $(\mathbf{P}, 2.52 \mathrm{~g})$ with $\mathrm{HBr}$ in the presence of $\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO}\right)_2 \mathrm{O}_2$ gives two isomeric bromides in a $9: 1$ ratio, with a combined yield of $50 \%$. Of these, the entire amount of the primary alkyl bromide was reacted with an appropriate amount of diethylamine followed by treatment with aq. $\mathrm{K}_2 \mathrm{CO}_3$ to give a non-ionic product $\mathbf{S}$ in $100 \%$ yield. The mass (in mg) of $\mathbf{S}$ obtained is $\underline{\hspace{2cm}}$. [Use molar mass (in $\mathrm{g} \mathrm{mol}^{-1}$) : $\mathrm{H}=1, \mathrm{C}=12, \mathrm{~N}=14, \mathrm{Br}=80$ ]