Private Engineering Company looking for animated 2D/3D videos of its skilling courses

I am looking for a series of isometric/animated videos of approximately 180 seconds each. These should be explanatory videos which talk about our engineering courses. The animated videos should explain the concepts of the course in a concise manner. My budget for the same is around USD $650 per video. If you are interested in the project, you need to first create a SHORT FREE DEMO VIDEO of around 20 seconds for me to see. If I am satisfied with the quality of your work, only then I will place an order. Please contact me only if you are willing to create a free demo video first and show me. The demo video should not be from your previous work; instead it should be made on the basis of details that I send you. Don't ask me to place an order before you show me demo video. Contact me only if you are willing to work as per my terms. Please read this request carefully before you contact me.