JEE Advanced 2023 Chemistry question on Haloalkanes and Haloarenes

The reaction of 4-methyloct-1-ene (P, 2.52 g) with HBr in the presence of $\text{(C}_6\text{H}_5\text{CO)}_2\text{O}_2$ 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. $\text{K}_2\text{CO}_3$ to give a non-ionic product S in 100% yield.

The mass (in mg) of S obtained is ___.

[Use molar mass (in g mol$^{-1}$): H = 1, C = 12, N = 14, Br = 80]