Local time differs from every 10 of longitude and the next by how many minutes?

At what season is the north of the Arctic Circle referred to as the “land of the midnight sun”?

Places 15° west of Greenwich will be how long behind Greenwich Mean Time?

At a point just north of the Arctic Circle there are twenty-four hours of darkness at the time the sun is directly overhead on which of the following latitudes? 

If a traveler leaves the U.S.A (W) at 5:00am on Wednesday 25th December and crosses the International Date Line he would arrive Japan (E) at 5:00am on which date?