Answer
$$0.28125$$
Work Step by Step
Given $$\int_0^3f(x)dx,\ \ |f''(x)|=2 $$
Since the maximum error is
$$ \left|f^{\prime \prime}(x)\right| \frac{(b-a)^{3}}{12 n^{2}}$$
Then
\begin{align*}
\left|f^{\prime \prime}(x)\right| \frac{(b-a)^{3}}{12 n^{2}}&\leq2 \frac{(3-0)^{3}}{12 (4)^{2}}\\
&=\leq 0.28125
\end{align*}