A flat steel plate is of trapezoidal form. The thickness of the plate is 15 mm and it tapers uniformly from a width of 60 mm to a width of 10 mm in a length of 300 mm. If the plate is under an axial force of 120 kN, the elongation of the plate is (Take E=2.04 x 105 N/mm) (a) 0.422 mm (b) 0.453 mm (c) 0.478 mm (d) 0.493 mm