An iron rod of length 2m and cross-sectional area of 50 mm2 is stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young’s modulus of iron rod is
(a) 19.6 x 1020 N / m2
(b) 19.6 x 1018 N / m2
(c) 19.6 x 1010 N / m2
(d)19.6 x 1015 N / m2
