$q_x=-k\frac{del{T}^{**}}{\text{d}\text{e}\text{l}\text{x}},q_y=-k\frac{del{T}^{**}}{\text{d}\text{e}\text{l}\text{y}}$ and $q=\sqrt[\phantom{2}]{q_x^2+q_y^2}$ calculate q by adding required code to the computer program given below.

Note in order to take numerical derivative of the function you can use:

$dfx=f.$dfunc$(x,0)$;

$dfy=f.$dfunc$(x,1)$

HOMOGENEOUS, STEADY STATE SOLUTION; CARTESIAN COORDINATES