Alex recalled learning about finding critical points and maxima/minima in his Thomas Calculus. He differentiated (f(x)) to get (f'(x) = 3x^2 - 12x + 9), then set (f'(x) = 0).
If you're looking for a narrative or story related to calculus or specifically to Thomas Calculus 13th Edition, I can certainly craft a fictional tale that incorporates elements of calculus or problem-solving in a creative way.
While having a PDF of the solutions is convenient, "copy-pasting" answers is a recipe for failing exams. To use the manual as a learning tool: