Some scientists take their boat, the Vollert, out to an artificial reef they are studying. Nice weather on the way out means they can travel at 12 knots, but a storm blows in and they can only travel at 5 knots on the way home. What was their average speed for the whole trip?	Choose the correct choice from the following answers
A) 6 knots  B) 2.5 knots  C) 17 knots  D) 7 knots  E) 8.5 knots
(12 knots +5 knots)/2 = 8.5 knots   Correct option is: 8.5 knots
<result>E</result>
Some scientists take their boat, the Vollert, out to an artificial reef they are studying. Nice weather on the way out means they can travel at 12 knots, but a storm blows in and they can only travel at 5 knots on the way home. What was their average speed for the whole trip?