Calculate the Change in the Standard Molar Entropy of Sulfur

Calculate the change in the standard molar entropy of sulfur trioxide gas, SO₃, when it is cooled from a temperature of 100 °C to 10 °C at a constant pressure of 1 bar. The standard molar constant-pressure heat capacity of sulfur trioxide is 50.1 J K^-1 mol^-1.

A) +7.81 J K^-1 mol^-1
B) -13.8 J K^-1 mol^-1
C) -115 J K^-1 mol^-1
D) -6.01 J K^-1 mol^-1