Final answer:
The subject of this question is Work and Energy (C). The work done by friction can be calculated using the formula: Work done by friction = force of friction x displacement.
Step-by-step explanation:
The subject of this question is Work and Energy (C). The question is asking about the work done on the sled by friction in both cases. To calculate the net work done by friction, we need to take into account the displacement and the force of friction. The work done by friction can be calculated using the formula:
Work done by friction = force of friction x displacement