A toy car travels along a straight, horizontal track. The graph below shows the car's position \(x\) as a function of time \(t\). The segment of the graph from \(t = 2.0 \text{ s}\) to \(t = 5.0 \text{ s}\) is linear.

What is the velocity of the toy car at time \(t = 4.0 \text{ s}\)?