For the pressure vessel in Example 1.2, calculate the total internal energy of the gas stored in the vessel.

Data From Example 1.2:

A pressure vessel that has a volume of \(10 \mathrm{~m}^{3}\) is used to store high-pressure air for operating a supersonic wind tunnel. If the air pressure and temperature inside the vessel are \(20 \mathrm{~atm}\) and \(300 \mathrm{~K}\), respectively, what is the mass of air stored in the vessel?