A thin rod of length 'L' is lying along the x-axis with its ends at $x=0andx=L$. Its linear density (mass/length) varies with x as $k(Lx )_{n}$, where n can be zero or any positive number. If the position $x_{CM}$ of the centre of mass of the rod is plotted against 'n', which of the following graph best approximates the dependence of $x_{CM}$ on n ?