A thin non-uniform rod of length \(L\) is positioned along the \(x\)-axis from \(x = 0\) to \(x = L\). The linear mass density of the rod varies quadratically according to the function \(\lambda(x) = \lambda_0\left(1 + \dfrac{x^2}{L^2}\right)\), where \(\lambda_0\) is a positive constant. Which of the following expressions represents the correct integral setup to determine the center of mass coordinate \(x_{\text{cm}}\) of the rod?