A brick wall ( = 0.016 ft 2 /h) with a thickness of 1 1/2 ft is

A brick wall (α = 0.016 ft²/h) with a thickness of 1 1/2 ft is initially at a uniform temperature of 80°F. How long, after the wall surfaces are raised to 300°F and 600°F, respectively, will it take for the temperature at the center of the wall to reach 300°F?