For educational purposes, I am seeking example problems in the realm of natural sciences, engineering, and business that satisfy the following criteria:
- Consider a one-dimensional real function $f$ (potentially with some parameters).
- The problem should involve finding extrema of $f$.
- It should be meaningful in this context to employ the first or second derivative test to confirm that the critical points identified are indeed extrema and to determine their nature (maximum/minimum). Importantly, this determination should not be evident through other means beforehand.
- The calculations should be manageable manually, suitable for an advanced high school or freshmen level.
- The problem should represent a realistic scenario in the specified field (natural sciences, engineering, or business), avoiding unrealistic constructions.