Contour question - Draw contours for In (xy) = c

Question

Can anyone explain me how to draw the contour for surface z = in(x y) where its in(x y) = z , and z = 0, 1, 4.

The in function is defined as

$$ y(x) =e^x/x $$

I don't have a graphing calculator. I already understand the sections are z = in x and z = in y.

But I am completely lost in how to draw the contour.

Answer 1

Mathematica program has this function ContourPlot3D

 a = 1.8; in[u_] = Exp[u]/u; ContourPlot3D[z == in [x y], { x, -a, a},{y, -a, a}, {z, -a, a}]

It shows intersections at not only for the level curves $z =$ const., but also for $x= $const., and $ y= $ const.