wood shop project is due and I'm not sure where to start

the goal of the project is to build a catapult that accurately launches a penny into a target that is places 10 feet away 20 times. the supplies are 20 inches of string, 6 inches of dowel, 2 rubber bands, 3 foot by 1 inch by 1 1/2 inch piece of wood, 1 popsicle stick, 1 index card, and unlimited nails, glue, and use of machinery. thank you!