(2) A slab of meat having 5 cm of thickness is placed into a freezer operating at -18 C. To determine the heat transfer coefficient in the freezer, a rectangular shaped plastic material with a thickness of 5 cm at 25C is used. The center temperature of plastic material after 5 h in the freezer is recorded as - 1.2 C, which is the initial freezing temperature of the meat. Physical properties of the plastic material and meat are given in the table below. Considering the Biot number is greater than 0.1, determine the required time in hours to freeze the meat. Plastic material Food 0.28 0.63 Physical property Thermal conductivity (W/mK) Density (kg/m) Heat capacity (kJ/kg,K) Water content (%) 1030 990 3.1 1.6 20