$20$ a Determine the theoretical flame temperature that can be attained by the combustion of methane with $20\%$ excess air. Air and methane enter at $298K$ and a pressure of $1$atm. The reaction is complete. $Hr=-890\mathrm{.}4k\frac{J}{m}$ole The mean heat capacities in $\frac{J}{?}$ molK are $62\mathrm{.}75$ for $C{O}_2,52\mathrm{.}96$ for $H_{2}O,38\mathrm{.}67$ for $O_2$ and $37\mathrm{.}13$ for $N_2$b