A Stress gauge located at C on the surface of the bone AB indicates that the average normal stress in the bone is 3.80 MPa when the bone is subjected to two 1200N forces as shown. Assuming the cross section of the bone at c to be annular (two concentric circles) and knowing that its outer diameter is 25 mm. Determine the inner diameter of the bones cross section at C. (The 2 1200N forces are pullling the bone apart at ends A and B, with the gauge at C in the middle of the length of the bone)