Answer
$T_2=140°F$
Work Step by Step
From the material balance:
$m_i-m_e=m_2-m_1,\quad m_e=m_1=0$
$m_i=m_2$
From the entropy balance
$m_2s_2-m_1s_1+m_es_e-m_is_i\geq0$
$m_2s_2-m_is_i\geq0$
$s_2\geq s_i$
Minimum temperature occurs at the equality:$s_2=s_i$
$s_2-s_i= c_p\ln\left(\dfrac{T_2}{T_1}\right)-R\ln\left(\dfrac{P_2}{P_1}\right)=0$
Constant pressure:
$\ln\left(\dfrac{T_2}{T_1}\right)=0$
$T_2=T_1=140°F$
