3-146 An oil pipeline and a 1.3-m³ rigid air tank are connected to each other by a manometer, as shown in Fig. P3-146. If the tank contains 15 kg of air at 80°C, determine (a) the absolute pressure in the pipeline and (b) the change in Ah when the temperature in the tank drops to 20°C. Assume the pressure in the oil pipeline to remain constant, and the air volume in the manometer to be negligible relative to the volume of the tank. Oil SG=2.68/ h = 75 cm 3D ↓ 1.3 m³ Air, 80°C Ah = 20 cm 50° D= 4 mm Mercury SG= 13.6