A boat anchored at sea is passed by twelve wave crests in a time of $180\ \text{s}$. The separation between neighbouring crests is $10\ \text{m}$. What is the speed of the wave?
- A$0.056\ \text{m s}^{-1}$
- B$0.67\ \text{m s}^{-1}$
- C$15\ \text{m s}^{-1}$
- D$18\ \text{m s}^{-1}$