(;
GM[1]
SZ[19]
AW[jc][pc][qf][ch]
AB[dc][cf][hc]
C[Problem 73. Black to play.  

Where should Black invade White's position on the right ? ]
(;B[nc]
TE[2]
C[Correct Answer.  

Black 1 aims at White's enclosure on the right. ]
;W[pe]
C[If White defends with 2, ... ]
;B[lc];W[je];B[mf]
C[... the moves to 5 are the normal development. <= ]
)
(;B[lc]
TE[2]
C[Correct Answer.  

Black 1 is also a vital point. ]
;W[nc]
C[White will answer with 2 and ... ]
;B[kd]
C[... Black attacks the white stone on the left with 3. <= ]
)
)