Example $1$:

A portion of a well$-$insulated duct in a ventilation system where the

pressure is very nearly $1$ bar throughout the system. Assuming the

ideal gas model for air with cp $1k\frac{J}{k}gK,$ and ignoring kinetic and

potential energy effects, determine:

$($a$)$ the temperature of the air at the exit,

$($b$)$ the exit diameter, in m

$($c$)$ the rate of entropy production within the duct, in min$)$

PLEASE EXPLAIN THE SOLUTION STEP BY STEP