Air is contained in a vertical cylinder fitted with a frictionless piston and a set of stops. The atmospheric pressure outside the cylinder is 83kPa. The diameter of the cylinder is 0.4m, the mass of the piston is 250kg, and the volume of the air inside the cylinder is 0.25m^3 when the piston is on the stops. Initially the piston is on the stops and the air in the cylinder is at 90kPa, 20 degrees celcius. The air in the cylinder is then heated to a final temperature of 100 degrees celcius. Model the air as an ideal gas. Find the pressure needed to lift the piston off the stops.