A rod $CD$ of thermal resistance $10.0\mathrm{~KW}^{-1}$ is joined at the middle of an identical rod $AB$ as shown in figure. The ends $A$, $B$ and $D$ are maintained at $200^{\circ}\mathrm{C}$, $100^{\circ}\mathrm{C}$ and $125^{\circ}\mathrm{C}$ respectively. The heat current in $CD$ is $P\mathrm{~W}$. The value of $P$ is $\_\_\_\_$.