Calculating Work Done by Gravity on a Moved Book

[talaroue]

Homework Statement

A 1.7 kg book is lying on a 0.99-m-high table. You pick it up and place it on a bookshelf 2.43 m above the floor.
How much work does gravity do on the book

Homework Equations

Wmg=mgYi-mgYf

The Attempt at a Solution

I thought that is the correct equation so I simply just plugged and chugged but it came out wrong. What did I do wrong?

 

[berkeman]

Homework Statement

A 1.7 kg book is lying on a 0.99-m-high table. You pick it up and place it on a bookshelf 2.43 m above the floor.
How much work does gravity do on the book

Homework Equations

Wmg=mgYi-mgYf

The Attempt at a Solution

I thought that is the correct equation so I simply just plugged and chugged but it came out wrong. What did I do wrong?

It might just be a sign error. Note that the question asks for the work done by gravity on the book. But the positive work done is by the person lifting the book...

 

[talaroue]

Sorry guys I jumped the gun on this one. I soon realized that I just had to reverse my orginal equation. The equation that I have is for the work done by your hands picking the book up.

 

[talaroue]

I just posted as you posted yeah, thanks for the help!