A heat source at T = 10^{3} K is connected to another heat reservoir at T = 10^{2 } K by a copper slab which is 1 m thick. Given that the thermal conductivity of copper is 0.1 WK^{–1} m^{–1}, the energy flux through it in the steady state is :

(1) 120 Wm^{–2 }

(2) 65 Wm^{–2 }

(3) 200 Wm^{–2 }

(4) 90 Wm^{–2}