Given coordinates represent three vertices of a parallelogram. Write the coordinates of each other point that could be the 4th.
a) (x1 + x3 - x2, y1 + y3 - y2)
b) (x1 + x2 - x3, y1 + y2 - y3)
c) (x2 + x3 - x1, y2 + y3 - y1)
d) (x1 + x3 + x2, y1 + y3 + y2)