All surfaces of an infinitely long heating element, having a cross section in the shape of a cross,.

All surfaces of an infinitely long heating element, having a
cross section in the shape of a cross, are maintained at 300 C. Due to
symmetry, only a quarter of the cross section is shown in the figure. Heat is
uniformly produced in the element at a rate of 100 kW/m 3. Find the
temperature distribution in the element at the locations shown in the figure.
The element thermal conductivity is 35 W/m·K. All surfaces are exposed to a
convection boundary condition of Tf = 40 C and h = 1200 W/m2
·C.