Everything is shown in the attached pictures.
Problem: THe first consideration in bicycle design is strength. stiffness matters, of course, but the initial design criterion is that the frame and forks should not collapse in normal use. The loading on the forks is predominantly bending. If the bicycle is for racing, mass is primary consideration: the forks should be as light as possible. WHat is the best material and shape? Table1 summarize the requirements of the problem.