People partially cool themselves by sweating, which releases water that evaporates. If during exercise a human “burns” 1000 kcal (4184 kJ) in one hour of exercise, how many grams of water must evaporate at a body temperature of 37^◦C? Assuming only 75 percent of the sweat evaporates (the rest being retained by the exercise clothes), how many grams of sweat must actually be produced?