Emily Stewart must decide whether to repair a fence around her garden or pay someone $300 to do it for her. If Emily repairs the fence, she could use some leftover fencing materials from a previous job. Those materials cost $60, but she cannot sell them and has no other use for them. In addition she would have to buy additional materials that would cost $100. Emily estimates that she would spend 15 hours purchasing the materials and repairing the fence. If she did not do the repairs herself, she could spend the time playing tennis. She values her tennis-playing time at $10 per hour. Should Emily make the fence or pay someone else to do it for her?