b$)$ Ethane is fed to a boiler where it is burnt with $50\%$ excess air. The ethane is supplied to the boiler at $25C$ and the combustion air at $50C.$

If $65\%$ of the energy from the combustion goes into raising steam what would be the stack temperature?

If $90\%$ of the energy from the combustion goes into raising steam, then what will be the difference in the stack temperature?

The heat of combustion of ethane at $25C$ is $-1428k\frac{J}{m}ol$ where the heat of combustion refers to each mole of fuel burnt with the standard state of reactant and products as gas. Assume that air consists of $21\%O_2$ and $79\%N_2$ on a volume basis.

Additional data:

$C_p(O_2)$:$30J(molC{)}^{-1}$

$C_p(N_2)$:$30J(molC{)}^{-1}$

$C_p(H_{2}O)$:$35J(molC{)}^{-1}$

$C_p(C{O}_2)$:$39J(molC{)}^{-1}$