Answer:
1747.9 J
Step-by-step explanation:
The work done to lift a book by a certain height
is

where
m = 1.40 kg is the mass of one book
is the acceleration due to gravity
The first shelf is 15.0 cm (0.15 m) from the ground, and it can be filled with 28 books. So, the work done to fill the first shelf is

The 2nd shelf is 38.0 cm above the first one, so its height from the ground is

It can also contain 28 books, so the work done to fill this shelf is

The height of the third shelf is

It can also contain 28 books, so the work done to fill this shelf is

The height of the 4th shelf is

It can also contain 28 books, so the work done to fill this shelf is

The height of the 5th shelf is

It can also contain 28 books, so the work done to fill this shelf is

Therefore, the total work done is:
