When you hold up a 100-N weight in your hand, with your forearm horizontal and your palm

Question:

When you hold up a 100-N weight in your hand, with your forearm horizontal and your palm up, the force exerted by your biceps is much larger than 100 N-perhaps as much as 1000 N. How can that be? What other forces are acting on your arm? Draw an FBD for the forearm, showing all of the forces. Assume that all the forces exerted on the forearm are purely vertical-either up or down.