If an analytical expression for the curve is available, useful relationships can be developed by differentiation. For example the form above, simplified slightly by putting CL0 = 0, has a maximum CL/CD at CL2 = CD0/K. For a propeller aircraft this is the maximum endurance condition and gives a speed of 185 km/h (115 mph). The corresponding maximum range condition is the maximum of CL3/2/CD, at CL2 = 3.CD0/K, and so the optimum speed is 244 km/h (152 mph).