If a mass $M$ produces an elongation of $\Delta L$ in a wire of radius $r$ and length $L$, then the Young's modulus of the material of the wire is given by:
(a) $Y=\frac{M g}{\left(\pi r^{2} \times \Delta L\right)}$
(b) $Y=\frac{M g \times \Delta L}{\left(\pi r^{2} \times L\right)}$
(c) $Y=\frac{M g \times L}{\left(\pi r^{2} \times \Delta L\right)}$
(d) $Y=\frac{M \times \Delta L}{\left(\pi r^{2} \times L\right)}$