For human survival, approximately what percentage of air must be oxygen?

Mrs. kirby, 58, is a moderately active woman. she works in the garden almost daily, occasionally walks with her friends, and babysits her three very active young grandchildren every weekend. she eats a fairly standard diet every day: she has cereal with milk and coffee for breakfast, some kind of salad for lunch, and a piece of meat or fish with a healthy of veggies for dinner. she usually skips desserts or has just a couple of strawberries. when asked to look at the food labels and calculate her intake of carbohydrates, fats, and proteins in grams over the entire day, on an average day, she came up with the following numbers: carbohydrates: 243 g fats: 41 g proteins: 63 g calculate what percentage of mrs. kirby's total energy intake came from carbohydrates.