Unit 1: Supply and demand criss cross

Thanks to tutor2u for this
http://www.tutor2u.net/blog/index.php/economics/comments/make-your-students-happy-test-their-demand-and-supply-knowledge-with-this-5?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+economics_news+%28tutor2u+Economics+Blog%29#When:11:49:00Z