i was also given info from my instructor that the answer should be about the center of mass from the birds beak... it didn’t really make sense to me so that’s why im asking for help lol

On a day when the barometer reads 75.23 cm, a reaction vessel holds 250 ml of ideal gas at 20 celsius. an oil manometer ( ρ= 810 kg/m^3) reads the pressure in the vessel to be 41 cm of oil and below atmospheric pressure. what volume will the gas occupy under s.t.p.?