Economics is Real... Part 1 of Many

I had a request the other day for a specific blog entry. Someone asked me how economics applies to real life.
Well, to all less educated in the ways of economics than myself and this individual:
In every way! Sheesh!
Thus follows today's discourse...
Actions should be undertaken if the marginal benefit is equal to or greater than the marginal cost.
Here's an example- I was doing a project for my Global Trading System class earlier this semester. There was one last question on the assignment that I knew was going to take me over an hour. This question was worth 5 marks out of 120. This assignment was worth 15% of my total grade. So, I could spend an extra hour (the marginal cost) to get an additional 0.625% in the class (the marginal benefit). Now, at ony other time, the hour wouldn't have been a big deal (ie. a large cost) but in this specific hour, my roommates were watching The Cutting Edge and I was missing it. An extra 0.625% is not worth an hour of The Cutting Edge. Maybe an hour of the rest of my life, but not a spectacle of ice skating set to 80's music.
I decided not to do it. Marginal cost exceeded marginal benefit.
Coming up next... Maximizing Utility Subject to a Budget Constraint! Or maybe the Phillips Curve!