(18 pts) A vertical piston-cylinder assembly contains air as shown on the next figure. A 6.4-kg piston on its top has a diameter of 90mm and is attached to a spring and exposed to an atmospheric pressure of 1.01 bar. Initially, the piston head is at a position such that the spring exerts no force on it. Then the valve is opened until the air pressure is at 400 kPa and the volume is 0.40 L. When the valve is further opened to let additional air in, the piston rises 2.0 cm more. Ignoring the friction between the piston and the cylinder wall, determine the pressure of the air within the cylinder when the piston is (a) in its initial position and (b) in its final position, in atm.