Xavier Aptitude Test 2019 Paper

Let C be a circle o f radius $\sqrt{20}$ cm. Let ${\mathit{l}}_1,{\mathit{l}}_2$ be the lines given by $2\mathit{x}-\mathit{y}-1=0$ and $\mathit{x}+2\mathit{y}-18=0$,respectively. Suppose that passes through the center of C and that ${\mathit{l}}_2$ is tangent to C at the point of intersection of ${\mathit{l}}_1$ and ${\mathit{l}}_2$. If (a, b) is the center of C, which of the following is a possible value of a + b?