$($c$)$ Consider the system shown in Figure Q$1($c$)$ below. If a change of $0\mathrm{.}9$kPa in the pressure

of air causes the brine$-$mercury interface in the right column to drop by $5mm$ in the

brine level in the right column while the pressure in the brine pipe remains constant,

determine the ratio of $\frac{A_2}{A_1}.$

$(10$ marks$)$

Figure Q$1($c$)$

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