4. A 0.04-mol ideal gas at a temperature of 300 K is contained in a vertical, frictionless pis- ton-cylinder device as shown in Fig. 2. The piston has a cross-sectional area of 35 cm. When the gas is at an equilibrium, the spring above the piston is stretched, exerting a force of 550 N on the piston, and the height of the gas in the cylinder is 15 cm. If the atmospheric pressure is 101 kPa, determine the mass of the piston in kg. 101 kPa atm A = 35 cm h = 15 cm Figure 2: Piston cylinder connected to a spring