$*57.$ A $63-$kg skier coasts up a snow$-$covered hill that makes an angle of $25]$ with the horizontal. The initial speed of the skier is $6\mathrm{.}6\frac{m}{s}.$ After coasting $1\mathrm{.}9$ m up the slope, the skier has a speed of $4\mathrm{.}4\frac{m}{s}.($a$)$ Find the work done by the kinetic frictional force that acts on the skis. $($b$)$ What is the magnitude of the kinetic frictional force?

Draw a picture and designate initial and final velocities and positions as well as all forces acting on the skier.

Which forces are internal conservative and which external and$/$or non$-$conservative?