The rectangle will be 3 units by 6 units so it will be 18 units^2
The larger lengths of the rectangle are discovered because 0,0 -> 0,6. The y value has increased by six units.
The smaller lengths of the rectangle can be determined by 0,0 -> 3,0. The x value has increased by 3 units.
If we needed to discover the last vertices, it would be at 3,6.