The rectangle has upper-left coordinates (3,-3), upper-right coordinates (7,-3) and area 16 square units.
By these coordinates, we know that it's base length is 7 - 3 = 4 units.
And, since the area of a rectangle is given by it's base length times its height h, which is: 4*h = 16, which implies h = 4 units.
Therefore, the botton coordinates will be (3,-3-4) = (3,-7) and (7,-3-4) = (7,-7)