6.8 WP Water contained in a closed, rigid tank, initially at 100 lbf/in., 800F, is cooled to a final state where the pressure is 20 lbf/in. Deter- mine the change in specific entropy, in Btu/lb R, and show the process on sketches of the T-v and T-s diagrams. ans: -0.9925 Btu/lb.R