Three statements are given, followed by four conclusions numbered I, II, III and IV. Assuming the statements to be true, even if they seem to be at variance with commonly known facts, decide which of the conclusions logically follow(s) from the statements.

Statements:

All books are pens.

All pens are erasers.

All erasers are files.

Conclusions:

I. All pens are files.

II. All pens are books.

III. All files are books.

IV. All files are pens.