Problem $2$: A heat engine that receives heat from a furnace at $1200C$ and rejects waste heat to a river at

$20C$ has a thermal efficiency of $40$ percent. Determine

$($a$)$ the second$-$law efficiency of this power plant.

$($b$)$ irreversibility rate of this process if the heat engine receives heat from the furnace at a rate of $400$

kW $.$