(c) 1, 3
The diagonals of a parallelogram bisect each other, therefore co-ordinates of mid-points of both the diagonals are the same co-ordinates of mid-point of diagonal AC
= \(\bigg(\frac{4-2}{2},\frac{b-1}{2}\bigg) \) = \(\bigg(1,\frac{b-1}{2}\bigg) \)
Co-ordinate of mid-point of diagonal BD
= \(\bigg(\frac{1+a}{2},\frac{2-0}{2}\bigg) \) = \(\bigg(\frac{1+a}{2},1\bigg) \)
⇒ \(\frac{1+a}{2}=1\) and \(\frac{b-1}{2}=1\)
⇒ 1 + a = 2 and b – 1 = 2
⇒ a = +1 and b = 3