Bookworm puzzle

[blamocur]

Two volumes of a famous author, the first and the second, are side-by-side on
a bookshelf. The pages of each volume are 2 cm thick, and the cover – front
and back each – is 2 mm. A bookworm has gnawed through (perpendicular to
the pages) from the first page of volume 1 to the last page of volume 2. How
long is the bookworm’s track?

 

[Deleted member 4993]

Two volumes of a famous author, the first and the second, are side-by-side on
a bookshelf. The pages of each volume are 2 cm thick, and the cover – front
and back each – is 2 mm. A bookworm has gnawed through (perpendicular to
the pages) from the first page of volume 1 to the last page of volume 2. How
long is the bookworm’s track?

I know the options but I am not telling !!!!

 

[Cubist]

Spoiler: I have my books placed like this

Spoiler: answer

4mm