import math
#calculate the change in entropy
#Initialization of variables
T2=920. #R
T1=520. #R
P1=14. #psia
P2=84. #psia
J=778.
R=53.35
cv=0.1715
N=1
#calculations
k= math.log(T2/T1) /math.log(P2/P1)
n=1/(1-k)
cx=cv+R/(J*(1-n))
dS=N*cx*math.log(T2/T1)
#results
print '%s %.5f %s' %("Change in entropy =",dS,"unit of entropy")