A spherical, cryosurgical probe may be imbedded in diseased tissue for the purpose of freezing, and thereby, destroying the tissue. Consider a probe of 3 mm diameter, whose surface is -30 degree C when imbedded in tissue that is at 37degree C. A spherical layer of frozen tissue forms around the probe, with a temperature of 0 degree C existing at the phase front (interface) between the frozen and normal tissue. If the thermal conductivity of the frozen tissue is approximately 1. 5 W/mK and heat transfer at the phase front may be characterized by an effective convection coefficient of 50 W/m2K, what is the thickness of the layer of frozen tissue?