A uniform rod of length $L$ has a mass per unit length $\lambda$ and area of cross-section $A .$ The elongation in the rod is $l$ due to its own weight if it is suspended from the ceiling of a room. The Young's modulus of the rod is
(A) $\frac{2 \lambda g L^{2}}{A l}$
(B) $\frac{\lambda g L^{2}}{2 A l}$
(C) $\frac{2 \lambda g L}{A l}$
(D) $\frac{\lambda g l^{2}}{A L}$