A vacuum gage at the intake duct to a fan gives a reading of 4.2 in….

A vacuum gage at the intake duct to a fan gives a reading of 4.2
in. of manometer fluid. The surrounding atmospheric pressure is
15.6 lbf/in.2 Determine the absolute pressure inside the duct, in
lbf/in.2 The density of the manometer fluid is 49.94 lb/ft3, and
the acceleration of gravity is 32.2 ft/s2.