A $12 \mathrm{in}$. ID gas pipeline carries methane (molecular weight $(M=16)$ at a rate of $20,000 \mathrm{scfm}$. The gas enters the line at a pressure of $500 \mathrm{psia}$, and a compressor station is located every 100 miles to boost the pressure back up to $500 \mathrm{psia}$. The pipeline is isothermal at $70^{\circ} \mathrm{F}$, and the compressors are adiabatic with an efficiency of 65%. What is the required horsepower for each compressor? Assume ideal gas behavior.