With the rider in the racing position, how much more power is required to pedal a bicycle at \(15 \mathrm{mph}\) into a \(20-\mathrm{mph}\) head-wind than at \(15 \mathrm{mph}\) through still air? Pedaling at \(15 \mathrm{mph}\) in still air, how much more power is required for an upright position instead of a racing position?