Four. The distance between location A and location B is 120 kilometers. A car travels from location A to location B at a speed of 30 kilometers per hour. 1. Write the function relationship between the distance \( s \) (kilometers) the car is from location B and the time \( t \) (hours) since it left location A, and determine the range of the independent variable. 2. Draw the graph, and indicate the distance the car is from location B after 2.5 hours of departure from location A. (10 points)
4. Solution:
1) The function relationship between $\mathrm{s}$ and $\mathrm{t}$ is $s=120-30 t$.
$$
(0 \leqslant \mathrm{t} \leqslant 4)
$$
2) Draw point A $(0, 120)$ and point B $(4,0)$,
then line segment $\mathrm{AB}$ is

the required graph (Figure 5).
From the graph, we can see: When $t=2.5$, $s=45$, that is, 2.5 hours after departing from location A, the car is 45 kilometers away from location B.