A bullet looses $\;(\large\frac{1}{n})^{th}\;$ of its velocity passing through one plank . The number of such planks that are required to stop the bullet can be :

Question

$(a)\;\large\frac{n^{2}}{2n-1}\qquad(b)\;\large\frac{2n^{2}}{2n-1}\qquad(c)\;\normalsize Infinite\qquad(d)\;n$