Graded Go Problems for Beginners volume 3 problem 21

[PeterPeter]

$$Bc
$$ +-------------------------
$$ | . . O . . O X . a . . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O b X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . . O X . a . . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O b X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

Black to play and win the capturing race.

A is given as the solution, but what is wrong with B?

[CnP]

I think it's because if black 1, then white 2

$$Bc
$$ +-------------------------
$$ | . . O . . O X . . 2 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . . O X . . 2 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

with one possible continuation leading to a ko

$$Bc
$$ +-------------------------
$$ | . . O . . O . 4 . O 3 .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O X X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . . O . 4 . O 3 .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O X X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

I could be wrong though and missing some killer sequence.

Thanks for posting the question though btw.

[1/7,000,000,000]

If white 2 then black captures f19.

[RBerenguel]

$$Bc
$$ +-------------------------
$$ | . . O . . O X . a . . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O b X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . . O X . a . . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O b X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

Black to play and win the capturing race.

A is given as the solution, but what is wrong with B?

I'm not thinking very clearly today (it's incredible how under-sleeping prevents my tsumego reading), but if b, what it white just takes? Seems to be a ko for B to lose after that

[rat4000]

Nope:

$$Bc
$$ +-------------------------
$$ | . . O . 4 O X 2 5 3 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . 4 O X 2 5 3 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

Looks like CnP's two-step ko is the best white gets. Still better than just losing though

[RBerenguel]

Nope:

$$Bc
$$ +-------------------------
$$ | . . O . 4 O X 2 5 3 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------------
$$ | . . O . 4 O X 2 5 3 . .
$$ | . . O X X X O O O X . .
$$ | . . . O O X O 1 X X . .
$$ | . . . , . X O X . , . .
$$ | . . O . O O X . . . . .
$$ | . . . . . . X . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . . . . . . . . . .
$$ | . . . , . . . . . , . .[/go]

Looks like CnP's two-step ko is the best white gets. Still better than just losing though

Right, I got up to here in some variation, but everything felt too blurry this morning