A 4 cm diameter potato, initially at 20 C, is dropped into boiling water at 100 C. The heat transfer coefficient between the water and surface is 3000 W/(m2K). Determine the time required for the centre of the potato to reach 95 C. The potato has a thermal conductivity of 0.68 W/(mK) and a thermal diffusivity of 1.610-7 m2/s