A composite rod ABC is made of two rods AB and BC of same cross-sectional area. Material of AB has coefficient of thermal conductivity K and that of rod BC is $\frac{\mathrm{k}}{2}$ . In steady state , temperature of junction B is

 

• A

  ${75}^{\mathrm{o}}\mathrm{C}$

• B

  $66.7^{\mathrm{o}}\mathrm{C}$

• C

  ${90}^{\mathrm{o}}\mathrm{C}$

• D

  $87.5^{\mathrm{o}}\mathrm{C}$