On 5 July, at 1200 zone time, you cross the 180th meridian steaming westward. What is your local time?

Correct Answer: Option C — It is 1200, 6 July.

Zenith distance is the angular distance from the zenith to a celestial body, calculated by subtracting the observed altitude (Ho) from 90° (90° - 47°50' = 42°10').