If the system of linear equations
x + y + z = 5 x + 2y + 2z = 6
x + 3y + λz = μ, (λ, μ ∈ R), has infinitely many solutions, then the value of λ + μ is :
(1) 10 (2) 9 (3) 12 (4) 7
Correct option (1) 10
Explanation: