1. **State the problem:** The maximum speed $S$ of a vehicle is partly constant and partly varies as the engine capacity $C$. Given two points: when $C=2000$, $S=240$ km/h and when $C=15000$, $S=200$ km/h, find $C$ when $S=300$ km/h. 2. **Form the equation:** Since $S$ is partly constant and partly varies as $C$, we write: $$S = kC + m$$ where $k$ and $m$ are constants. 3. **Use the given points to form equations:** For $C=2000$, $S=240$: $$240 = k \times 2000 + m$$ For $C=15000$, $S=200$: $$200 = k \times 15000 + m$$ 4. **Solve the system:** Subtract the second equation from the first: $$240 - 200 = 2000k - 15000k$$ $$40 = -13000k$$ $$k = -\frac{40}{13000} = -\frac{4}{1300} = -0.0030769$$ 5. **Find $m$ using one equation:** $$240 = -0.0030769 \times 2000 + m$$ $$240 = -6.1538 + m$$ $$m = 240 + 6.1538 = 246.1538$$ 6. **Write the full equation:** $$S = -0.0030769 C + 246.1538$$ 7. **Find $C$ when $S=300$:** $$300 = -0.0030769 C + 246.1538$$ $$300 - 246.1538 = -0.0030769 C$$ $$53.8462 = -0.0030769 C$$ $$C = \frac{53.8462}{-0.0030769} = -17500$$ 8. **Interpretation:** The negative capacity is not physically meaningful, so the model suggests no real engine capacity yields $S=300$ km/h under this linear assumption. **Final answer:** No positive engine capacity $C$ satisfies $S=300$ km/h with the given model.