An oven has a wall made of three materials (materials A, B, and C) lined one after the other. The inside of the oven has an air temperature of 200˚C, with a convective heat transfer coefficient of 10 Wm-2 K-1 . Material A is in immediate contact with this hot air, with a thickness of 0.2 m, and a thermal conductivity of kA = 45 Wm-1 K-1 . Material B has an unknown thickness (LB), with a thermal conductivity of kB = 1 Wm-1 K-1 . Material C is 0.1 m thick with a thermal conductivity of kC = 10 Wm-1 K-1 . If you measure the outer surface temperature of the material C as Ts,2 = 20˚C and the outer surface temperature of material A as Ts,1 = 170˚C, estimate the thickness of material B (LB).