2. A continuous random variable \(X\) has the probability density function
$$\begin{array} { l l }
\mathrm { f } ( x ) = k & 5 \leq x \leq 15 ,
\mathrm { f } ( x ) = 0 & \text { otherwise. }
\end{array}$$
- Find \(k\) and specify the cumulative density function \(\mathrm { F } ( x )\).
- Write down the value of \(\mathrm { P } ( X < 8 )\).