Write a main function and the following functions to compute

Write a main function and the following functions to compute the stress and strain in a steel rod of diameter D (inches) and length L (inches) subject to the compression loads P of 10,000 to 1,000,000 lbs. in increments of 100,000 pounds. The modulus of elasticity E for steel is 30 x 10^6
Function to compute stress from the formulas