A 5-lb roast initial at 70°F is placed in an oven at 350°F. You may assume the heat transfer coefficient is 2.5 Btu/hr.ft2. °F and the thermal conductivity of the roast can be considered the same as that of water. Roast can be considered as a spherical shape and it is consider to be cooked when the center temperature reaches 200°F. Estimate the cooking time.