A ship travels due North at a speed of $20\,\text{m s}^{-1}$. Water current then starts flowing from East to West, with speed $20\,\text{m s}^{-1}$. What is the magnitude of the ship’s resultant velocity?
- A$0\,\text{m s}^{-1}$
- B$20\,\text{m s}^{-1}$
- C$28\,\text{m s}^{-1}$
- D$40\,\text{m s}^{-1}$