A copper rod AB of length 100 cm is fixed with a steel rod BC of length 20 cm at B . If the ends A and C are maintained at temperature $\;100^{0}C\;$ and $\;0^{0}C\;$ , then the temperature of the function B is : [thermal conductivities of copper and steel are 0.9 and 0.18 CGS units respectively ]

Question

$(a)\;40^{0}C\qquad(b)\;60^{0}C\qquad(c)\;80^{0}C\qquad(d)\;50^{0}C$