An engineer uses a bolt to connect a joint. The force provided by the bolt F is a function of the external load P that it must bear. The bolt applies a force of 200 lb against an external load of 100 lb. The same bolt must apply a force of 400 lb against an external load of 600 lb. Find the joint constant C, and preload Fi (in lb), that satisfies the linear equation describing the force, F = CP + Fi.

F = P +