Question $3$

An isothermal $(T=-28\mathrm{.}5$ Celsius$)$ gas tank has a height of $131m.$ The gas pressure at the bottom of the tank is $4\mathrm{.}75$ bar, and at the top of the tank, the pressure is measured to be $4\mathrm{.}51$ bar. What is the molecular weight of the gas in this tank, in $\frac{g}{m}ol?$