A cylinder having a piston restrained by a linear spring (of spring constant 15 kN/m) contains 0.5 kg of saturated vapor water at 120°C. Heat is transferred to the water, causing the piston to rise, and during the process the spring resisting force is proportional to the distance moved. The piston cross-sectional area is 0.05 m2. What is the pressure in the cylinder when the temperature inside reaches 600°C?