3. A piston-cylinder device containing hydrogen at 14.7 psia with a cross-sectional area of 4.2 ft? and a volume of 19 ft³ has an uncompressed linear spring (k= 16000 Ibf/ft) attached. The hydrogen is heated until the volume doubles. What is the a.) final pressure b.) total work done by the hydrogen, and c.) fraction of the total work done by the spring. ANS[134.378 psia, 210.4 Btu]