Ethane $($C$2$H$6)$ is burned with $20$ percent excess air during a combustion process.

Assuming complete combustion and a total pressure of $100$ kPa, determine

$($a$).(6$ pt$)$ The air$$fuel ratio, AF$.$

$($b$).(3$ pt$)$ The dew$-$point temperature of the products, Tdp$.$