What is the area of the rectangle ABCD with vertices A(-6,3), B(2,5), C(3,1), D(-5,-1)?

The perimeter of a rectangle doesn't tell you its dimensions, so there are
an infinite number of different dimensions and different areas it could have
with the same perimeter.  I'm pretty sure there's some more information in
the part of the question that you skipped over before you started copying
the part that you posted.