This is not a homework question, I'm just curious. Suppose you had a sailboat sailing on calm water. Let's say the sailboat is capable of sailing at 10 knots under the current wind conditions using only its sails. Now say the sailboat had a small propeller motor that was capable of propelling the boat at 5 knots under its own power without help from the sails. If the boat was at full sail, and you ran the motor at the same time, would the boat reach a speed of 15 knots? Would it stay at 10 knots since the motor could not propel the boat above 5? Or would the speed actually decrease to below 10 knots due to the friction between the motor and the water?