When the object reaches the bottom of the inclined plane,its total energy is purely kinetic,considering horizontal to be the reference level.
And,the energy value is
Now,total energy on top of the inclined plane was purely potential energy as the object was at rest,and its value was
So,total energy at the beginning of the journey was
So,this decrease in total energy value suggests that it must have been utilized to overcome the frictional force,
And the value is