Problem of the Week--January 30

Please help me. I would like to make a geometry bulletin board that has a border of circles, triangles and squares. I know that 20 shapes will fit across the board and that 12 shapes will fit down the board. If I start in the top left-hand corner with a circle, followed by a triangle, then a square, and repeat this pattern all around the board, how many of each shape will I need?