Well.. really easy problem. That's why i was surprised when black played at R19
(;AP[goproblems]AB[qa]AB[pb]AB[qc]AB[rc]AB[oc]AB[nc]AB[mc]AB[nb]AB[na]AB[oa]AB[ma]AB[md]AW[nd]AW[od]AW[pd]AW[pc]AW[qd]AB[rd]AW[qe]AW[re]AW[qb]AW[rb]AW[me]AW[le]AW[ld]AW[lc]AW[lb]AW[la]AW[mb]AW[kb]AB[jb]AB[kc]AB[kd]AB[jd]AB[qf]AB[ra]MA[ra]TR[rb]C[Black carelessly anwsered whites marked stone with the marked black stone.. punish him for his great mistake.](;W[sb]C[Right. so simple...RIGHT];B[sa](;W[pa]C[RIGHT])(;W[sc];B[sd])(;W[sd];B[sc]))(;W[sd];B[sb])(;W[sc];B[sb])(;W[sa];B[sb])(;W[se];B[sb]))