4 The delay, in hours, of certain flights from Australia may be modelled by the continuous random variable \(T\), with probability density function $$\mathrm { f } ( t ) = \left\{ \begin{array} { c c } \frac { 2 } { 15 } t & 0 \leqslant t \leqslant 3
1 - \frac { 1 } { 5 } t & 3 \leqslant t \leqslant 5
0 & \text { otherwise } \end{array} \right.$$

1. Sketch the graph of f.
2. Calculate:
   1. \(\mathrm { P } ( T \leqslant 2 )\);
   2. \(\mathrm { P } ( 2 < T < 4 )\).
3. Determine \(\mathrm { E } ( T )\).