You are turning 78 RPM, with a propeller pitch of 21 feet, and an estimated slip of -7%. What is the speed of advance?

Correct Answer: Option C — 17.3 knots

Negative slip indicates the vessel advances faster than theoretical pitch travel due to wake suction effects. Applying a -7% slip factor (1.07) to 78 RPM and a 21-foot pitch produces a speed of advance of 17.3 knots following standard Bowditch calculations.