Question

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

Answer 1

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.

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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.