please solve using specific weight

Q$\mathrm{.}2\mathrm{.}57$ The mercury manometer of Fig. P$2\mathrm{.}57$ indicates a differen$-$

tial reading of $0\mathrm{.}30$ m when the pressure in pipe $A$ is $30-mmHg$

vacuum. Determine the pressure in pipe $B.$

Figure P$2\mathrm{.}57$