Let $K$ be a positive definite $n \times n$ matrix with eigenvalues $\lambda_1 \geq \lambda_2 \geq \cdots \geq \lambda_n>0$. For what values of $\varepsilon$ does the iterative system $\mathbf{u}^{(k+1)}=\mathbf{u}^{(k)}+\varepsilon \mathbf{r}^{(k)}$, where $\mathbf{r}^{(k)}=\mathbf{f}-K \mathbf{u}^{(k)}$ is the current residual vector, converge to the solution to the linear system $K \mathbf{u}=\mathbf{f}$ ? What is the optimal value of $\varepsilon$, and what is the convergence rate?