A mercury manometer (Æ¿ = 13,600 kg/m3) is connected to an air duct to measure the pressure

Question:

A mercury manometer (Æ¿ = 13,600 kg/m3) is connected to an air duct to measure the pressure inside. The difference in the manometer levels is 15 mm, and the atmospheric pressure is 100 kPa.
(a) Judging from Fig. P1-67, determine if the pressure in the duct is above or below the atmospheric pressure.
(b) Determine the absolute pressure in the duct.