(;
GM[1]
SZ[19]
AW[oc][qd]
AB[jc][mc][qf][qi]
C[Problem 105. Black to play.  

The small-knight enclosure secures the corner, but if Black has built strong positions around it, an invasion is possible. Where should Black invade ? ]
(;B[pc]
TE[2]
C[Correct Answer.  

Black 1 is the point to gauge out White's base. ]
;W[pd];B[qc]
(;W[od];B[rd];W[re];B[rc];W[qe];B[rf];W[se];B[ob];W[nb];B[pb]
C[Up to 13, Black lives in the corner. ]
;W[nc];B[mb]
C[After 15, however, White's group is eyeless and will become a target of attack. <= ]
)
(;W[pb]
C[Failure.  

White might respond with 4 ... ]
;B[qb];W[ob]
C[... and 6 here. ]
;B[rd];W[re];B[rc];W[qe]
C[However, after she defends with 10, ... ]
;B[od]
C[... Black cuts with 11 and White's position collapses. <= ]
))
(;B[at])
)