Hello, i desperately need some help! Need to get it done for tomorrows class but i haven't got a clue how to script it. Please look at the image so its easier to explain.

http://oi39.tinypic.com/35872hk.jpg

Okay, so how do i make it that when i choose the category and the quantity i get a calculation in the total box?

Here's what i did: http://oi41.tinypic.com/34hchl1.jpg

However, it doesn't work Please helpppp!