Hard friction question

Hi, I'm struggling to answer this question as this isn't like the only question where you need to find the angle of inclination, I would greatly appreciate any help.

Thanks in advance.

Any thoughts? How would you normally proceed with a box on a slope type question? What do the two possible values of alpha relate to? What have you been able to do so far?

Normally I would get the forces up and down the slope and equate them since they're in limiting equillibrium, I then re-arrange and get tan(alpha) = some expression, but this not only gives the wrong answer, but there should be another answer that i'm still missing.

Resolving up/down the plane when in equilibrium will work.

Don't forget there are two possible limiting equilibria, on the point of sliding down the slope, and ....

Post working if you'd like someone to check it.

Hi, I'm struggling to answer this question as this isn't like the only question where you need to find the angle of inclination, I would greatly appreciate any help.

Thanks in advance.