The answer is 4 but idk how to get it so can somebody explain how to get it

How much gravitational potential energy does the block have
when it gets to the top of the ramp ?

      (weight) x (height) = (15 N) x (0.2 m)  =  3 Joules .

If there were no friction, you would only need to do 3 Joules of work
to lift the block from the bottom to the top.

But the question says you actually have to do 4 Joules of work
to get the job done.

Friction stole one of your Joules along the way.

Choice-4 is not the correct one.
Choice-1 is the correct one.



Notice that the mass of the block is NOT  15 kg , and you
don't have to worry about gravity to answer this question.

The formula for potential energy is  (m)·(g)·(h) .
But (m·g) is just the WEIGHT, and the formula
is actually (weight)·(height).
The question GIVES us the weight of the block . . . 15 N .
So the potential energy at the top is just (15N)·(0.2m) = 3 Joules.