Is there more to the question?
It is given that the triangles ITH and APG are congruent.
When the two triangles are congruent, then the corresponding angles and sides are congruent to each other.
By being congruent, the corresponding angles which are congruent are:

Therefore, 
SO, Option 2 is the correct answer.

Thickness of the book is ~
Refer to the attachment for solution ~