I recently read an obituary of Paul MacCready, the father of human powered aircraft. He invented the Gossamer Albatross, an aircraft which successfully flew the English Channel under human power (a cyclist turning the propeller). The aircraft flew from Folkestone, England to Cap Griz Nez, France, a distance of 22 miles, in approximately 3 hours fighting a headwind. On the return trip, this headwind would become a tailwind. Let us assume that the cyclist can pedal at a rate of 12 mi / hr without wind interference. Exhibit a rational expression for the round trip time, Folkestone to Cap Griz Nez and back, as a function of wind speed. What would be the domain of this rational expression?