Kyu Exercise 57 / Solution

Black kills  

Black kills with .

White first

White makes ko (5 at 1)  

If white had just one outside liberty, she could squeeze with at a (connect-and-die). But as it is, there is only ko.

Inferior  

here is inferior. Although there is still a ko, takes the ko first.

thanatos13: 5 at a makes white live, doesn't it? at a is self-atari.