A wire suspended vertically from one of its ends is stretched by attaching a weight of $200 \mathrm{~N}$ to the lower end. The weight stretches the wire by $1 \mathrm{~mm}$. The elastic energy stored in the wire is
(A) $0.2 \mathrm{~J}$
(B) $10 \mathrm{~J}$
(C) $20 \mathrm{~J}$
(D) $0.1 \mathrm{~J}$