The liquid in the open tube manometer is mercury, y1=3cm and y2 = 7cm. Atmospheric pressure is 980mbrs. (A) what is the absolute pressure at the bottom of the U-shape tube? (B) what is the absolute pressure in the open tube at a depth of 4 cm below the free surface? (C) what is the absolute pressure of the gas in the tank? (D) what is the gauge pressure of the gas in pascal