Consider a 2-km-deep gas well containing a gas mixture of methane and ethane at a uniform temperature

Question:

Consider a 2-km-deep gas well containing a gas mixture of methane and ethane at a uniform temperature of 30C. The pressure at the top of the well is 14 MPa, and the composition on a mole basis is 90% methane, 10% ethane. Determine the pressure and composition at the bottom of the well, assuming an ideal gas mixture.