(a) What is the efficiency of an uut-ufcondition professor who does 2.30 x 105 J of usetul work while metabolizing 500 kcal of food energy? (Enter your answer as a percentage. Enter a number.) {in} How many food calories [in kcal) would a welliconditioned athlete metabolize in doing the same work with an efficiency of 20%? {Enter a number.)