To find the global maximum value of the function on the closed interval [0, 3], we first compute the derivative of \( f(x) \):
\[
f'(x) = 3x^2 - 9x + 6
\]
We then solve for critical points by setting \( f'(x) = 0 \) and solving for \( x \):
\[
3x^2 - 9x + 6 = 0
\]
Solving the quadratic equation, we get the critical points.
Next, we evaluate \( f(x) \) at the critical points and at the endpoints of the interval \( x = 0 \) and \( x = 3 \).
After evaluating, we find that the maximum value of \( f(x) \) is \( 2.5 \). Hence, the correct answer is \( 2.5 \).