A speedboat travels from the dock to the first buoy, a distance of 20 meters, in 18 seconds. It began the trip at a speed of o m/s. By the time it reached the buoy, it was going 10 m/s. What was the average velocity of the boat?
A) -3.33 m/s^2
B) -1.11 m/s
C) +1.11 m/s
D) +3.33 m/s