A lunch tray is being held in one hand, as the figure illustrates. The mass of the tray itself is 0.167 kg, and its center of gravity is located at its geometrical center. On the tray are a 1.11-kg plate of food and a 0.262-kg cup of coffee. Get (a) the force exerted by the four fingers (b) the force exerted by the thumb. Both forces act perpendicular to the tray, which is being held parallel to the ground.