You may use the Antoine equation given below to predict the vapour pressure of water:

$ln{P}^{**}(kPa)=A-\frac{B}{C+T(C)},A=16\mathrm{.}3872,B=3885\mathrm{.}70,C=230\mathrm{.}170$

In experiments on an internal combustion engine, petrol $($use $C_8{H}_{18}$ as an approximation for petrol$),$ is combusted with excess air. The dewpoint of the combustion products $($at $P_{\text{a}\text{t}\text{m}}=90$kPa $)$ is measured as $48C.$ Use a basis of $1$kmol of petrol and estimate the amount of excess air $($dry$)$ that is fed to the engine. You may use the Antoine equation given in Tut $2\mathrm{.}3$ for vapour pressure data of water.

a$)$ Use the Antoine constants given in $3)$ for vapour pressure data

b$)$ Use steam tables for vapour pressure data

For this question I need the answer as a percentage of excess dry O$2$