Write a program to compute the diameter in centimeters of a steel rod, an aluminum rod, and a copper rod which can withstand a particular compression load. The allowable compression stress of steel, aluminum, and copper is 25,000lbs/m², 15,000 lbs/m², and 20,000lbs/m², respectively.
Area of rod = compression load/Allowable compression stress
Area = A=πr^2 where diameter d=2r