(;
GM[1]
SZ[19]
AW[jc][pc][qe][qj]
AB[cd][ec][hc]
C[Problem 78. Black to play.  

White has made wide extensions from her corner enclosure at the top right. However, White's position is thin  and vulnerable. Where should Black invade ? ]
;B[lc]
TE[2]
C[Correct Answer.  

Black 1 is the correct invasion point. ]
(;W[je];B[le];W[jg]
LB[je:2]
C[If White jumps to 2 and 4, ... ]
;B[lg]
LB[le:3]
C[... Black follows her into the center with 3 and 5. <= ]
)
(;W[kd]
C[Variation.  

White might also attack with 2. ]
(;B[oc]
C[Black would then attach with 3 and, ... ]
;W[pd];B[pb]
C[... after 5, ... ]
;W[qb];B[me]
C[... jump to 7. <= ]
)
(;B[me]
C[If Black 3 here, ... ]
;W[nc]
C[... White would attack at 4. <= ]
))
)