One of the way to find the area is the following.
First you have to find width and length of the rectangle. To do that you can use formula
d= √(x2-x1)^2+(y2-y1)^2
You have A(−4, 0), B(−3, 1), C(0, −2), D(−1, −3) and find |AB| and |BC|, Then the area would be |AB|*|BC|