Below is the graph of a trigonometric function. It has a minimum point at $\left(-\frac{1}{2} \pi, 2.4\right)$ and a maximum point at $\left(\frac{3}{2} \pi, 13\right)$. What is the amplitude of the function?

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: Below is the graph of a trigonometric function. It has a minimum point at $\left(-\frac{1}{2} \pi, 2.4\right)$ and a maximum point at $\left(\frac{3}{2} \pi, 13\right)$. What is the amplitude of the function?

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: Below is the graph of a trigonometric function. It has a minimum point at $\left(-\frac{1}{2} \pi, 2.4\right)$ and a maximum point at $\left(\frac{3}{2} \pi, 13\right)$. What is the amplitude of the function?
