Selling Back Books

I just got back from selling back some of my books. I decided to keep my Spanish and Biology books because I'm sure they will come in handy in the future. I tried to sell back my Writing and Math books but they didn't take back all of my writing books. What the heck? The four books and one CD come as a pack. Why wouldn't you take them all? That's ridiculous! Now I'm stuck with two essay sample books and a computer CD about "visualizing argument." What am I going to do with them? Nothing. If anybody wants them let me know.