List of top Signals and Systems Questions on Continuous-Time Signal Representation and Area Under a Signal

Let \[ f(t)= \begin{cases} 1, & t\in[0,2] \\ -t+3, & t\in[2,3] \\ 0, & \text{otherwise} \end{cases} \] Then \[ \int_{-\infty}^{\infty} f(\tau)\,d\tau = \_\_\_\_\_. \] (rounded off to one decimal place)