1. **State the problem:** We are given a linear cost function for hiring a scooter: $$C = 0.15t + 22$$ where $C$ is the cost in pounds and $t$ is the time in minutes. 2. **Understand the formula:** This is a linear equation in the form $$C = mt + b$$ where $m = 0.15$ is the rate of change (cost per minute) and $b = 22$ is the fixed starting cost. 3. **Interpret the graph:** The graph shows the cost starting near 22 pounds at $t=0$ and increasing linearly as time increases, consistent with the equation. 4. **Calculate cost at specific times:** For example, at $t=160$ minutes, $$C = 0.15 \times 160 + 22 = 24 + 22 = 46$$ pounds. 5. **Summary:** The cost increases by 15 pence per minute after a fixed charge of 22 pounds. This matches the graph's description and the given equation.