Number of triangles that can be formed from the points on 3 of the sides. 5C17C16C1+5C17C19C1+5C16C19C1 +6C17C19C1 =210+315+270+378 ⇒α=1173 Number of quadrilaterals that can be formed by taking one point from each of the four vertex 5C17C16C19C1=5×6×7×9=1890 ⇒β=1890 ∴β−α=1890−1173 =717