It is required to insulate a kitchen oven with cork board (K = 0.043 W/(m K)) so that the heat losses from the oven does not exceed 400 W/m$$^2$$ when the inner surface of the oven is at $$225^\circ C$$ and the outer surface of the oven is at $$40^\circ C$$. The thickness of insulation required is nearly

A

1 cm

B

2 cm

C

3 cm

D

4 cm