6.4 mol ideal gas consisting of non-linear molecules at a pressure of 3.7 bar, a volume of 2.2 m³ undergoes an isothermal pressure change up to a pressure of 6.9 bar without exchanging heat with the environment. What is the change in entropy of this gas? Select the correct answer from the following list:

a) -.166e-1 kJ/K

b) .249e-1 kJ/K

c) 49.7 J/K

d) -33.2 J/K