A hot-air balloon is travelling vertically upward at a steady speed of $3.00\,\text{m s}^{-1}$. A sandbag is released from the balloon. It takes $5.00\,\text{s}$ for the sandbag to reach the ground. How high was the balloon when the sandbag was let go?
- A$29\,\text{m}$
- B$108\,\text{m}$
- C$123\,\text{m}$
- D$138\,\text{m}$