A plane wall of thickness L is subjected to convection at both surfaces with ambient tempe...

A plane wall of thickness L is subjected to convection at both surfaces with ambient temperature T∞1 and heat transfer coefficient h1 at inner surface, and corresponding T∞2 and h2 values at the outer surface. Taking the positive direction of x to be from the inner surface to the outer surface, the correct expression for the convection boundary condition is

(a)

(b)

(c)

(d)

(e) None of them