One rock is projected vertically upwards from Earth’s surface, while an identical rock is projected vertically upwards from Mars’ surface. In each case, the rock is given an initial velocity of $12\,\text{m s}^{-1}$. Each rock then rises to its greatest height above the surface and later falls back to the surface. The velocity-time graph for each rock is shown. For both rocks, air resistance is negligible. What is the difference between the maximum heights reached by the two rocks?
- A$12\,\text{m}$
- B$15\,\text{m}$
- C$19\,\text{m}$
- D$24\,\text{m}$