For saving energy, bicycling and walking are far more efficient means of transportation than is travel by automobile. For example, when riding at mi/h, a cyclist uses food energy at a rate of about kcal/h above what he would use if merely sitting still. (In exercise physiology, power is often measured in kcal/h rather than in watts. Here 1 kcal 5 1 nutritionist's Calorie = 4 186 J.) Walking at mi/h requires about kcal/h. It is interesting to compare these values with the energy consumption required for travel by car. Gasoline yields about J/gal. Find the fuel economy in equivalent miles per gallon for a person (a) walking and (b) bicycling.