Air is contained in a vertical cylinder fitted with a frictionless piston and two sets of stops. The volume is 0.5m^3 when the piston is on the lower stops, and 0.7m^3 when against the upper stops. The pressure of the air must be 110kPa to support the piston when it is between stops. Initially the air is at 90kPa, 10 degrees celcius, and the piston is on the lower stops. The air is then heated until the piston is pushed agains the upper stops and the pressure of the air in the cylinder is 140kPa. Model the air as an ideal gas. Find the mass of the air in the cylinder.