At 1524 ZT on 14 June, in DR position LAT 30°51'N, LONG 30° 02'W, you observe an amplitude of the Moon. The center of the Moon is on the visible horizon and bears 103.9°pgc. The variation is 10°W. What is the gyro error?

Correct Answer: Option B — 2.0°E

Gyro error is determined by comparing the computed true amplitude of the Moon at the visible horizon against the observed gyrocompass bearing. Using standard navigational sight reduction tables, the difference confirms a gyro error of 2.0°E.