Your vessel receives a distress call from a vessel reporting her position at LAT 5°24'N, LONG 31°16'W. Your position is LAT 2°39'S, LONG 39°24'W. Determine the distance from your vessel to the vessel in distress by Mercator sailing.

Correct Answer: Option D — 688.7 miles

Mercator sailing resolves long distances crossing the equator by utilizing meridional parts. Using latitude difference, meridional difference ($m$), and difference of longitude between the vessel and the distress position computes a true rhumb line distance of 688.7 miles.