Answer
$\Delta s =-0.105\ kJ/kg.K$
Work Step by Step
$\Delta s = c_v\ln\left(\dfrac{T_2}{T_1}\right)+R\ln\left(\dfrac{v_2}{v_1}\right)$
$T_{avg}=429\ K\small\rightarrow c_p=0.690\ kJ/kg.K,\ R=0.2598\ kJ/kg.K$
Given $T_1=298\ K,\ T_2=560\ K,\ v_1=0.8\ m^3/kg,\ v_2=0.1\ m^3/kg$
$\Delta s =-0.105\ kJ/kg.K$
