Consider the fiberglass insulation in a kitchen oven, which is sandwiched between two sheets of…

Consider the fiberglass insulation in a kitchen oven, which
is sandwiched between two sheets of metal. The maximum temperature on the inside
surface of the oven may reach 260 C. Find the minimum thickness of the
fiberglass insulation to ensure that the temperature on the outside surface of
the oven does not exceed 40 C. The kitchen temperature varies between 18 C to
37 C. The heat transfer coefficient between the oven surface and the kitchen is
15 W/m2 ·K. The thermal conductivity of fiberglass is kfiberglass
= 0.04 W/m·K.