Water entering the pipes in the boiler of a power plant at a temperature of $100$C with a mass flow rate of $100$ kg$/$s$.$ It comes out of the pipes at $200$C at a constant pressure of $0\mathrm{.}8$MPa. Burnt gases passing through the pipes remain constant. It cools from $1060$C to $540$C at pressure. Burnt gases can be considered like air, which is an ideal gas. Heat transfer from the boiler to the environment is negligible. Kinetics and potential under steady conditions Neglecting the change in energies, $($To$=25$C$,$ Po$=1$ atm should be taken.$)$

a$)$ Mass flow rate of combustion gases $($kg$/$s$),$

b$)$ Exergy destruction per unit time $($kW$),$

c$)$ Calculate the exergetic efficiency.