EVENT
BOARDSIZE 19
SETUP W K17 O16 
SETUP B D16 F17 Q15 R17 R10 
COM
Reference Diagram to Problem 11. White to play.  

Where should White play in the upper right corner ?
ENDCOM
W 1 Q17
MARK A@M17
COM
Correct Answer.

To appreciate just how big Black's invasion at A is, suppose
White played 1 ...
ENDCOM
B 2 Q16
W 3 P17
COM
... and 3 first.
ENDCOM
B 4 R18
W 5 O14
COM
After 5, White has a large territory at the top and she is also
threatening to invade the right side.
<=
ENDCOM