1. **State the problem:** We need to find the cost to deliver a container a distance of 30 km given the cost-distance relationship shown by the graph. 2. **Identify known points:** From the graph, two points are given: $(0, 500)$ and $(40, 800)$ where the first coordinate is distance $d$ in km and the second is cost $C$. 3. **Find the equation of the line:** The cost $C$ varies linearly with distance $d$. The slope $m$ is given by $$m = \frac{800 - 500}{40 - 0} = \frac{300}{40} = 7.5$$ 4. **Write the linear equation:** Using point-slope form with point $(0, 500)$, $$C = 7.5d + 500$$ 5. **Calculate cost at $d=30$ km:** $$C = 7.5 \times 30 + 500 = 225 + 500 = 725$$ 6. **Interpretation:** The cost to deliver a container 30 km is 725.