From your 0100 position, you change course to 258° per standard magnetic compass. Your engine speed is 10.0 knots. A short time later, your fathometer reads 51 feet (15.5 meters) under the keel. What is the water depth?

A
42.5 feet (12.9 meters)
B
51.0 feet (15.5 meters)
C
59.5 feet (18.0 meters)
D
60.4 feet (18.4 meters)
E