Art value?

Hello, I drew a little horsie for someones CAM, and I'm not sure what amount I should ask for payment... I sent them a picture of the horse before it was finished, so it still had the background intact, so the original person got someone else to actually make the CA with the CAM, and she finished it up, so it looks a tad different then the final one I sent them. Here is my original- So the question remains: What should I ask for this?