15. A partial oxidation is carried out by bubbling air through a batch of liquid in a pressurized reactor 3m in diameter and 5m tall. The initial liquid level is 4.0m, as shown by a manometer connected to the top and bottom of the reactor. During aeration the liquid level is expected to rise 10 to 20 percent, depending on the air flow rate, but the manometer reading is found to be unchanged when the air is turned on. (a) Explain why the manometer reading does not change when the liquid is aerated. (b) Show that the installation of a second manometer, suitably located, would permit calculation of the height of the aerated liquid. State what assumptions are involved