$3[3$ marks$]$ A closed cylindrical tank filled with water has a spherical dome and is connected to a piping system as shown. The liquid in the top part of the piping system has a specific gravity of $0\mathrm{.}8,$ and the remaining parts of the system are filled with water. If the gauge pressure at A is $60$ kPa $,$ provide an expression for the absolute pressure in pipe $Bp{B}_B$ as a function of ${}_w$ and $g.$