Rate of flow of heat in path $BCA$ will be same
i.e. ${\left( {\frac{Q}{t}} \right)_{BC}} = {\left( {\frac{Q}{t}} \right)_{CA}}$
$ \Rightarrow \frac{{k(\sqrt 2 T - {T_C})A}}{a} = \frac{{k({T_C} - T)A}}{{\sqrt 2 a}}$
$ \Rightarrow \frac{{{T_C}}}{T} = \frac{3}{{1 + \sqrt 2 }}$




