Tony is trying to lift a heavy box with his back, as shown in the image below. (a) Determine the magnitude of the force in the back muscles, Fback, required to support his upper body as well as the box. Note the 8 cm indicated on the diagram is the lever arm associated with Fback about the pivot point indicated. The mass of Tony's upper body is 55.0 kg and the mass of the box is 30.0 kg. (b) Calculate and comment on the ratio of the force exerted on Tony's back relative to his own weight. (c) Determine the magnitude and direction of the force exerted by Tony's vertebrae on the spine at the indicated pivot point