Two previously undeformed cylindrical specimens 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 15 mm and 13 mm, respectively. The second specimen, with an initial radius of 14 mm, must have the same deformed hardness as the first specimen; compute the second specimen's radius, in mm, after deformation.