You've done this workout four times by now, so you know how it goes, but don't let familiarity breed laziness. Every single exercise should be done with precision and a strong mind-muscle connection. Perform every crunch, twist, and raise with a clear picture in your mind of your abdominals doing the work.
When you're done crushing your core, hop onto a piece cardio equipment for a 50-minute ride. If you get bored, switch machines every 10 minutes or so!