Matrices and Determinants: JEE Main 2019 Mathematics question

If the system of linear equations x + y + z = 5 x + 2y + 2z = 6 x + 3y + $\lambda$z = $\mu$, ($\lambda$, $\mu$ $\in$ R), has infinitely many solutions, then the value of $\lambda$ + $\mu$ is :