(;AW[pa]AW[qa]AW[qb]AW[qc]AW[rc]AW[sc]AW[rd]AW[se]AW[sf]AW[rf]AW[qf]AW[qg]AW[qh]AB[rh]AB[sg]AB[ph]AB[pg]AB[pf]AB[pe]AB[qe]AB[re]AB[qd]AB[pc]AB[pb]AB[ob]AB[oa]AW[ri]AW[rj]AW[qj]AW[qk]AW[pk]AW[sk]AW[sl]AW[rl]AW[rm]AW[qm]AW[sm]AW[sn]AW[so]AB[sp]AB[rq]AB[sr]AB[rs]AB[qr]AB[qq]AB[ro]AB[rn]AB[qn]AB[qo]AB[pm]AB[pl]AB[ql]AB[ok]AB[pj]AB[pi]AB[qi]AB[nl]AB[nm]AB[nj]AW[pn]AW[on]AB[nn]AB[oo]AB[po]AB[ra]TR[ra]C[Black just played the marked stone as a ko threat for a 7 point ko. Should white answer?]LB[nd:Tenuki]AP[goproblems]
(;W[si]C[13 points for white. Nice ;)RIGHT])
(;W[rb];B[sa];W[sb];B[si];W[sd];B[sa]C[Seki.])
(;W[sb];B[si];W[sd];B[sa];W[rb];B[sa])
(;W[sj];B[sh];W[sd];B[sb]C[Seki.])
(;W[rg];B[sd])
(;W[sd];B[sb];W[si]C[Correct but w T16 is unnecessary.RIGHT])
(;W[nd];B[si];W[sd];B[sb]C[White lost 13 points :(]))