(;AB[jb]AB[jc]AB[ka]AB[kd]AB[ke]AB[le]AB[lg]AW[kb]AW[kc]AW[ld]AW[md]AW[me]AW[nf]AW[pf]AW[pc]AW[qi]TR[ka]C[Black wants to invade with the triangled stone. White to defend. Assuming sente is worthless.]AP[goproblems]
(;W[lb];B[la];W[ma];B[ja];W[mb]C[RIGHT])
(;W[la];B[lb];W[ja];B[lc];W[ka];B[ma]C[Oh no!])
(;W[mb]C[A bit too far.]
(;B[lb];W[lc];B[la];W[ma];B[ja]C[])
(;B[ma];W[lb];B[la];W[na];B[ja]C[])))