If the points P(a

We know that the diagonals of a parallelogram bisect each other

So the coordinates of the mid – point of the PR = Coordinates of the mid – point of the QS

{(2 + a)/2,(15 – 11)/2} = {(5 + 1)/2,(b + 1)/2}

2 + a = 6

a = 4

15 – 11 = b + 1

4 = b + 1

b = 3

Hence, a = 4, b = 3