the friction is a force which has an effect opposite to the force which causes a motion (the motion can be zero!). The value of the friction depends on the normal force to the surface on which a solid is moving.
With your problem the weight of the skier causes a normal force to the snow and an accelerating force. Now the friction decreases this accelerating force. (see attachment)
Let be the weight of the skier
be the normal force
the accelrating force and
Then you have:
. That means:
With a uniformly accelrated movement you have:
. You know the distance already and the accelration:
and . That means when the skier arrived at the edge.
Now the horizontal speed doesn't change but the vertical speed increases because the skier is falling down:
Use to calculate the time the skier is flying through the air:
. Plug in the values you know:
solve for t. I've got
Therefore the final speed is
. Approximately 38.4 km/h