Question: \(f(x)\) is a probability density function given by the formula below. Find the probability \(\Pr \left( 1\le X\le 3 \right)\)

\[f(x)=\left\{ \begin{aligned} & \text{ }\frac{2}{25}\left( 5-x \right)\text{ if }0\le x\le 5 \\ & \\ & \text{ }0\text{ otherwise} \\ \end{aligned} \right.\]