Which of the following reagents,when heated with ethyl chloride,produces ethylene?

The structure of product $(A)$ is:

The major products $X$ and $Y$ respectively from the following reactions are:

$A$ compound $(a)$,$C_8H_9Br$,gives a white precipitate when heated with alcoholic $AgNO_3$. Oxidation of $(a)$ gives an acid $(b)$. The acid $(b)$,$C_8H_6O_4$,easily forms an anhydride on heating. Identify the compound $(a)$.

The most reactive molecules towards $SN^1$ reaction are:

$2-$bromopentane is heated with potassium ethoxide in ethanol. The major product obtained is