A plate product of 12cm in thickness, initially at 40C, is suddenly exposed to an environment of 4C. The surface heat transfer coefficient h is 16W/(m2K). The product properties are: =1100kg/m3,C=3.54kJ/(kgK), and k=0.85W/(mK). (1) Determine its thermal diffusivity, if it takes 2.5h for the center temperature of the product to reach 15C;(2) What is the center temperature at 1.5h ? Use the Heisler chart below. ( 10 points)