A closed tank contains $0.5$ m thick layer of mercury (specific gravity $=13.6$) at the bottom. A $2.0$ m thick layer of water lies above the mercury layer. A $3.0$ m thick layer of oil (specific gravity $=0.6$) lies above the water layer. The space above the oil layer contains air under pressure. The gauge pressure at the bottom of the tank is $196.2 \: kN/m^2$. The density of water is $1000 \: kg/m^3$ and the acceleration due to gravity is $9.81 \: m/s^2$. The value of pressure in the air space is

1. $92.214 \: kN/m^2$
2. $95.644 \: kN/m^2$
3. $98.922 \: kN/m^2$
4. $99.321 \: kN/m^2$