To move a heavy object a few feet in height, the incline plane is the most efficient device (of those listed) to use.

6/3 = 200/E
6E = 600
E = 100

A proportioning valve is commonly used on a vehicle equipped with front disc and rear drum-type brakes.
The valve reduces hydraulic pressure to the rear drum brakes to prevent rear wheel lockup and skidding during heavy brake pedal application.

The formula to determine the mechanical advantage of an incline plane is Length of 8/4 = 400/E
8E = 1,600
8E/8 = 1,600/8
E = 200