JEE Advanced 2023 Chemistry question

The reaction of 4-methyloct-1-ene (**P**, 2.52 g) with HBr in the presence of 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. to give a non-ionic product **S** in 100% yield. The mass (in mg) of **S** obtained is . [Use molar mass (in g mol): H = 1, C = 12, N = 14, Br = 80]