$4\mathrm{.}10$ Tim's $1993$ Buick has a six$-$cylinder, four$-$stroke cycle SI engine with multipoint port fuel injectors operating on an Otto cycle at WOT. The fuel injectors are set to deliver an AF such that gasoline would burn at stoichiometric conditions. $($Approximate gasoline using isooctane properties.$)$

Calculate:

$($a$)$ Equivalence ratio of air$-$gasoline mixture.

$($b$)$ Equivalence ratio if gasoline is replaced with ethanol without readjusting the AF delivered by the fuel injectors.

$($c$)$ Increase or decrease in brake power using alcohol instead of gasoline under these conditions, with the same air flow rate and same thermal efficiency. Assume ethanol would burn under these conditions with the same combustion efficiency. $[\%]$