A:If you have access to a gym... you can do the elliptical for 15 minutes. If not, you can go outside and run. Then I would do 3 sets of 30 situps, 3 sets of 10 push-ups (or you can use machines, if you have access to a gym)... and stretches for the last 3 or so minutes. 30 minutes isn't very long but you can get some good exercise in.
