Determine the change in entropy for the following:
a) Water, u=1000 kJ/kg, T=140 degree C to saturated liquid at p=3 bar
b) Air, T(1)= 500 degrees R, p(1)= 10 lbf/in^2 to T(2)= 900 degrees R, p(2)= 50lbf/in^2 (using air property tables and specific heat method)
c) Unused engine oil, T(1)=25 degrees F to T(2)= 45 degrees F