M14; 2D plot for 2 variable function - one variable constant

Hi All,

I have a stress equation that is a function of both X and Z (horizontal distance and depth).

I want to produce a 2D plot of this function with a constant X and a variable Z.  When I use the 2D plot and input the range variable 'z' on the vertical axis and stress(100,z) it does not give me the correct results. 

Any ideas?