A child slides down a snow-covered slope on a sled. At the top of the hill, her mother gives her a push at a speed of 1.5 m/s to get her started. The frictional force acting on the sled is one-fifth of the combined weight of the sled and the child. If she travels for a distance of 23.9 m and her speed at the bottom is 2.6 m/s, compute the angle that the hill makes with the horizontal.