The time taken by an object to down \( 45^\circ \) rough inclined plane is \( n \) times as it takes to slide down a perfectly smooth \( 45^\circ \) incline plane. The coefficient of kinetic friction between the object and the in line plane is:
\( 1 + \frac{1}{n^{2}} \)
\( \sqrt{\frac{1}{1-n^{2}}} \)
\( \sqrt{1-\frac{1}{n^{2}}} \)
\( 1 - \frac{1}{n^{2}} \)