A small sphere of reference-grade iron with a specific heat of 447 J/kgK and a mass of 0.515 kg is suddenly immersed in a water-ice mixture. Fine thermocouple wires suspend the sphere and the temperature is observed to change from 15°C to 14°C in 6.35 s. The experiment is repeated with a metallic sphere of the same diameter, but unknown composition with a mass of 1.263 kg. If the same observed temperature change occurs in 4.59 s, what is the specific heat of the unknown material?