Answer:
see below
Step-by-step explanation:
The covers ( there are 2) are
2* .9 mm = 1.8 mm
Depending on how they are defining pages
If they are defining pages as the number of papers
400 pages at .13 =
400 *.13 = 52 mm
total = 2 covers + 400 pages
= 1.8 + 52
53.8 mm
If they are defining pages as the page numbers
Each page number is on the front and back so 400/2 = 200 pieces of paper
200 pages at .13 =
200 *.13 = 26 mm
total = 2 covers + 400 pages
= 1.8 + 26
27.8 mm
