A wire of length $L$ and area of cross-section $A$, is stretched by a load. The elongation produced in the wire is $\angle$ If $Y$ is the Young's modulus of the naterial of the wire, then the force constant of the wire is
(a) $\frac{Y Z}{A}$
(b) $\frac{Y}{A}$
(c) $\frac{Y A}{L}$
(d) $\frac{Y A}{l}$