The Higher Critical Point

A cubic function is given by

$f(x) = 2x^3 - 15x^2 + 24x + 6$

Its graph flattens out at exactly two places — the two critical points.

Task: find both critical points, take the one with the larger $x$-value, and report the height of the curve there, i.e. the value of $f$ at that point.

Give an exact integer. The answer may be negative.