9.28 Two previously undeformed cylindrical speci- mens of an alloy are to be strain hardened by reducing their cross-sectional areas (while maintaining their circular cross sections). For one specimen, the initial and deformed radii are 17 mm and 12 mm, respectively. The second specimen, with an initial radius of 13 mm, must have the same deformed hardness as the first specimen; compute the second specimen's ra- dius after deformation