Help with this problem

[Cynosure]

I can't figure this out for the life of me. Black to play. I feel like there's a way to outright kill, but the best result I can think of results in ko.

[gamesorry]

I think the best result for black is indeed a ko...

[Solomon]

Unfortunately, the best you'll get is ko .

[Bill Spight]

Finding ko is excellent on your part.

But there are two kos. Do you see both of them?

Edit: Oops! I see that there is a third ko, but with a suboptimal .

Oh, dear, there's another one!

But there is only one with best play by White. This is a problem for both sides.