(;
GM[1]
SZ[19]
AW[cf][hc][he][bd][ke]
AB[pj][dj][dp][pd][pp][dd][fd][kc][ff][md]
LB[cf:1][fd:2][hc:3][kc:4][he:5][ff:6][ke:7][md:8][bd:9]
C[Problem 84. Black to play.  

White has just slid into the corner with 9. How should Black respond ? ]
;B[cc]
TE[2]
C[Correct Answer.  

Black should play 1, ... ]
;W[dh]
C[... forcing White to defend her stones on the left with 2. ]
(;B[hg]
C[Black then attacks the white stones at the top by playing on the vital point of 3, ... ]
;W[jc];B[jb];W[kb];B[lb];W[kd]
C[... so White has to make shape with the sequence to 8. ]
;B[lc];W[ib];B[gb]
C[Finally, Black can take the territory in the upper left corner with 11 in sente, ... ]
;W[ja];B[qd]
C[... then enclose the upper right corner with 13, to take a substantial lead. <= ]
)
(;B[jc]
C[The vital point.  

Black 3 is another vital point which robs White of her base, but ... ]
;W[hg]
C[... White can jump lightly to 4, putting pressure on Black's stones in the upper left. <= ]
)
)
