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 $10^{\circ}C$.Lengths of the copper, brass and steel rods are $46, 13 \;and \;12\; cms$ respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivies of copper, brass and steel are $0.92, 0.26\; and\; 0.12$ CGS units respectively. Rate of heat flow through copper rod is

Question

$\begin{array}{1 1}(A)\;4.8\;cal/s \\ (B)\;6.0\;cal/s \\(C)\;1.2 \;cal/s \\(D)\;2.4\;cal/s \end{array}$