# Three rods of Copper , Brass and Steel are welded together to form a Y - shaped structure . Area of cross - section of each rod = $\;4\;cm^{2}\;$ .End of copper rod is maintained at $\;100^{0}C\;$ where as ends of brass and steel kept at $\;0^{0}C\;$ .Lengths of the copper ,brass and steel rods are 46,13 and 12 cms respectively . The rods are thermally insulated from surroundings expect at ends . Thermal conductivities of copper , brass and steel are 0.92 , 0.26 and 0.12 CGS units respectively . Rate of heat flow through copper rod is :$\;\tau$

$(a)\;1.2\;cal/s \qquad(b)\;2.4\;cal/s\qquad(c)\;4.8\;cal/s\qquad(d)\;6.0\;cal/s$