I was not able to solve this myself. While I recalled that the "calculus of variations", e.g., the use of Lagrange Multipliers, is often used for such optimizations, I had forgotten how they worked. That is given
here.
A very friendly solution to this nice problem is
here.
Be sure to see the second article about outreach and The Little Prince.
The second article also references a purely calculus-based solution.
But, I wish I has done it myself!
Edited on January 10, 2019, 1:28 am