Answer:a
Explanation:
We have to lift the load two loads up one story, so energy required is
let m be the mass of each load and h is the height of each story
Energy 

Here energy gained is the potential energy which depends upon the datum(floor).
For lifting one load up one story
Energy required

thus
is half of 
So option a is correct
200N
Explanation:
600N-400N = 200N
<span>The screw is really just an inclined plane covered around with a tiny pole. The wedge is definitely an inclined plane, since it starts with a point, then rises getting thicker, as an inclined plane. </span>
I think its " both have level surfaces"