The Gap Between Eigenvalues

The matrix $A=\begin{pmatrix}20&20\\20&26\end{pmatrix}$ has eigenvalues $\lambda_1>\lambda_2$. Find $\lambda_1-\lambda_2$. \\ The answer is in the form $a\sqrt{b}$ for where $a$ and $b$ are positive integers, and $b$ is square-free. Input the answer as the sum $a+b$.