An ice figure skater starts out spinning at 0.89 revolutions per second with her arms outstretched. She wears lightly weighted bracelets to enhance the pin-up effect when she pulls her arms in. Where does this added energy come from?
a) The additional energy comes from the friction.
b) The additional energy comes from work done by the heat from the surrounding space.
c) The additional energy comes from work done by the skater's muscles.