For a fixed amount of a gas at a constant temperature, the volume of the gas is inversely proportional to its pressure. At a pressure of 30 pounds per square inch (psi), a gas has a volume of 600 in.3.Which function can be used to model the volume of the gas y, in cubic inches, when the pressure is x psi? y = 20xy = 18,000xy =20/x✔ y =18,000/x