${?}^{n}0$ A thin stick is placed along the $x$ axis so that one of its ends is at $x_1=0\mathrm{.}00m$ and the other one at $x_2=3\mathrm{.}85m.$ The stick has a non$-$uniform mass density $(x)=ax+b,$ where $a=0\mathrm{.}219k\frac{g}{m^2}$ and $b=1\mathrm{.}272k\frac{g}{m}.$

What is the $x$ coordinate $x_{cm}$ of the stick's center of mass?

$x_{cm}=$