A stent is a cylindrical tube, often made of metal mesh, that’s inserted into a blood vessel to overcome a constriction. It’s sometimes necessary to heat the stent after insertion to prevent cell growth that could cause the constriction to recur. One method is to place the patient in a changing magnetic field, so that induced currents heat the stent. Consider a stainless-steel stent 12 mm long by 4.5 mm in diameter, with total resistance 41 mΩ. Treating the stent as a wire loop in the optimum orientation, find the rate of change of magnetic field needed for a heating power of 250 mW.