hello.. Can u help me please,

A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25◦ with the
horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0m down the plane,
the mechanical energy of the Earth-block system changes by:
A. 0
B. −9.8J
C. 9.8J
D. −18 J
E. 18 J

Question

hello.. Can u help me please,

A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25◦ with the
horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0m down the plane,
the mechanical energy of the Earth-block system changes by:
A. 0
B. −9.8J
C. 9.8J
D. −18 J
E. 18 J

anonymous · Answer

Are you familiar with the formulas of mechanical energy ?

anonymous · Answer

You might notice that, mechanical energy of a system is conserved if there are no external nonconservative force acting on the system. 
In this case, there is one such force that is nonconservative: friction.
Do you need further help?

anonymous · Answer

thanks, I know the answer>> it's (-9.8 J)

first i find the height:
$$h= d \sin 25ْ$$

then I find the magnitude of PE=mgh

after that, using the Newton 2nd law find the net force

then I find KE=-FD

anonymous · Answer

Note that you could also skip all that considering that they are conserved and just find the work done by friction as it isn't conserved. :) Nice work .