Two conducting slabs having same shape and size  of heat conductivities k₁ and k₂ joined as shown in figure. The temperature at ends of the slabs are ${\mathrm{\theta }}_1$ and ${\mathrm{\theta }}_2$ (${\mathrm{\theta }}_1>{\mathrm{\theta }}_2$). The final temperature of junction (${\mathrm{\theta }}_{\mathrm{m}}$ ) is:
 

• A

  $\frac{{\mathrm{k}}_1{\mathrm{\theta }}_1+{\mathrm{k}}_2{\mathrm{\theta }}_2}{{\mathrm{k}}_1+{\mathrm{k}}_2}$

• B

  $\frac{{\mathrm{k}}_1{\mathrm{\theta }}_2+{\mathrm{k}}_2{\mathrm{\theta }}_1}{{\mathrm{k}}_1+{\mathrm{k}}_2}$

• C

  $\frac{{\mathrm{k}}_1{\mathrm{\theta }}_2-{\mathrm{k}}_2{\mathrm{\theta }}_1}{{\mathrm{k}}_1+{\mathrm{k}}_2}$

• D

  none of these