A 10 kg migratory swan cruises at 20 m/s. A calculation that takes into ac- count the necessary forces shows that this motion requires 200 W of mechanical power. If we assume an efficiency similar to humans (say, 25%), a reasonable assumption, then the metabolic power of the swan is significantly higher than this. The swan does not stop to eat during a long day of flying; it get the energy it needs from fat stores. Assuming an efficiency similar to humans, after 12 hours of flight, a. How far has the swan traveled? b. What fraction of its body mass does it lose? Assume that I g of fat contains 37 kJ of energy.