1.1. A ferry sails in a straight line from the harbour at $O$ to its destination $B$, passing the checkpoint $A$ on the way.
Figure 1 shows the displacement–time graph for the journey.
Displacement, $s$ is measured in metres from $O$, and time $t$ is measured in seconds.

Using the information in Figure 1, calculate the constant velocity of the ferry while it is travelling from $A$ to $B$.

1.2. Find the average speed of the ferry as it travels from $O$ to $B$.

1.3. The ferry company would like the journey to be completed within a maximum time of 25 minutes. Find, to three significant figures, the average speed the ferry would need to travel at in order to achieve this.