Derive the energy balance equation for a corner control volume in a three-dimensional steady conduction problem with

Question:

Derive the energy balance equation for a corner control volume in a three-dimensional steady conduction problem with heat generation in a rectangular coordinate system. Assume an adiabatic boundary condition and equal node spacing in all three dimensions.

GIVEN

Three-dimensional steady conduction in a rectangular coordinate system, corner boundary control volume with specified temperature boundarycondition