Answer
See answer below.
Work Step by Step
Eq. 7-26:
$ds=\dfrac{dh}T-\dfrac{vdP}T$
Since $dh=c_pdT$ and $v=RT/P$:
$ds=c_p\dfrac{dT}T-\dfrac{RT}P\dfrac{dP}T$
$ds=c_p\dfrac{dT}T-R\dfrac{dP}P$
$\Delta s = c_p\ln\left(\dfrac{T_2}{T_1}\right)-R\ln\left(\dfrac{P_2}{P_1}\right)$
