Two materials having coefficients of thermal conductivity '3k' and 'k' and thickness 'd' and '3d' respectively, are joined to form a slab as shown in the figures. The temperatures of the outer surfaces are `theta_(2)` and `theta_(1)` respectively `(theta_(2) gt theta_(2))`. The temperature at the interface is :

Options

A. `(theta_(1))/10+(9theta_(2))/10`
B. `(theta_(2)+theta_(1))/2`
C. `(theta_(1))/6+(5theta_(2))/6`
D. `(theta_(1))/3+(2theta_(2))/3`

Answer

A