IP An 81.0 kg in-line skater does 3620 J of non conservative work by pushing against the ground with his skates. In addition, friction does -665 J of non conservative work on the skater. The skater's initial and final speeds are 2.70 m/s and 1.22 m/s, respectively. 

(a) Has the skater gone uphill, downhill, or remained at the same level? Explain.

(b) Calculate the change in height of the skater.