A camera drone with mass $1.20\,\text{kg}$ remains stationary in the air at a particular point above the ground. The drone is fitted with four propellers. During a period of $1.00\,\text{s}$, each propeller drives $0.400\,\text{kg}$ of air straight downwards. Take the air above the propellers to be at rest. What is the speed of the air as it leaves each propeller?
- A$0.750\,\text{m s}^{-1}$
- B$3.00\,\text{m s}^{-1}$
- C$7.36\,\text{m s}^{-1}$
- D$29.4\,\text{m s}^{-1}$