The maximum value of the function $f(x) = 3x^3 - 18x^2 + 27x - 40$ on the set $S = \{x \in \mathbb{R} \mid x^2 + 30 \le 11x\}$ is
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Calculus Tip: When finding absolute extrema on a closed interval $[a,b]$, if the function lacks critical points inside the interval, the maximum and minimum will strictly lie on the boundary points $x=a$ and $x=b$.