A U$-$tube monometer is connected to a closed talk, shown below, containing oil having a density of $\backslash (850\backslash$mathrm$\{$~kg$\}/\backslash$mathrm$\{$m$\}3\backslash ),$ the pressure of the air above the oil being $3200$ Pa $.$ If the pressure at point A in the oil is $18000$ Pa and manometer fluid has a $\backslash (2800\backslash$mathrm$\{$~kg$\}/\backslash$mathrm$\{$m$\}3\backslash ),$ determine,

$1.$The depth of oil $\backslash ($ z $1\backslash )$

$2.$The differential reading, $\backslash ($ z $2\backslash )$ on the monometer