Hello, vixsta101!
Did you make a sketch?
Code:

 (3,3)
*    +      o  *
:  C :
D o(2,5)  :
:  :
:  :
:  :
+++
: O :
:  :
:  B:
:  o(4,1)
: A  :
*  o          *
(1,3)

We can "walk" our way through this . . .
Going from vertex to vertex , we move 5 units right and 1 unit up.
Going from vertex to vertex , we move 1 unit left and 5 units up. .(Why?)
. . Hence: .
Going from vertex C to vertex D, we move 5 units left and 1 unit down.
. . Hence: .