5-18E Hydrogen is contained in a piston-cylinder device at 14.7 psia and 15 ft’. At this state, a linear spring (F « x) with a spring constant of 15,000 lbf/ft is touching the piston but exerts no force on it. The cross-sectional area of the piston is 3 f?. Heat is transferred to the hydrogen, causing it to expand until its vol- ume doubles. Determine (a) the final pressure, (b) the total work done by the hydrogen, and (c) the fraction of this work done! against the spring. Also, show the process on a P-V diagram.