What is the minimum size iron pipe that can be used for an 121′ length, .5 psi piping system designed to carry 525 cf/hr of gas. Gravity is .6 with a total pressure drop of ½” water column?

What is the minimum size iron pipe that can be used for an 121′ length, .5 psi piping system designed to carry 525 cf/hr of gas. Gravity is .6 with a total pressure drop of ½” water column?