linear algebra - Finding out the number solutions for an equation system.

I'm currently doing an exercise where I should solve the equation system:

ax + y + az = 2

x + ay + z = 2
x + az = 1

and then answer "for which values on a does the equation system only have on solution? For which values on a do we have an infinite amount of solutions, and what value on a lacks solutions.

After solving the equation system I got this as an answer:

Now, how do I solve for which values on a does the equation system only have on solution? For which values on a do we have an infinite amount of solutions, and what value on a lacks solutions.