Can a Category D first mate be demoted to become a sailor?

Category D first mate can of course be demoted to become a sailor. The rules are as follows:

1.

You cannot be assigned to a higher position at a lower level, and you cannot be assigned to a higher position at a lower level.

2.

A first-class mate can serve as first mate, second mate, third mate and sailor on a second-class ship;

3.

But a second-class captain can only serve as a sailor on a first-class ship.