Black to save as many points as he can. Ignore the center - think only about groups on the edges and corners.
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[5.50]TM[]
PW[White]PB[Black]AW[oa][eb][fb][hb][nb][ob][ec][gc][ic][mc][oc][pc][qc][rc][sc][bd][cd][dd][id][jd][kd][ld][md][be][ee][af][bg][cg][ch][ci][ei][dj][ck][dk][dl][cm][em][cn][bo][co][qo][ep][fp][gp][hp][ip][qp][cq][eq][iq][kq][oq][pq][dr][jr]AB[pa][db][ib][jb][lb][mb][pb][qb][rb][sb][bc][cc][dc][jc][kc][lc][bh][bi][bj][cj][bk][bl][cl][bm][bn][rp][fq][gq][hq][qq][er][ir][qr][es][is]C[Black to live with as many groups as possible, with optimum result - center can be ignored.]
(;B[gr]CR[gr]
;W[an]CR[an]C[Comb formation is alive, so playing G2 is worth -1 in gote + white kills B6 group])
(;B[gs]CR[gs]
;W[an]CR[an]C[Comb formation is alive, so playing G1 is worth -1 in gote + white kills B6 group])
(;B[sq]CR[sq]
;W[an]CR[an]C[Tripod group is alive, so playing T3 is worth -1 in gote + white kills B6 group])
(;B[sr]CR[sr]
;W[an]CR[an]C[Tripod group is alive, so playing T2 is worth -1 in gote + white kills B6 group])
(;B[rr]CR[rr]
;W[an]CR[an]C[Tripod group is alive, so playing S2 is worth -1 in gote + white kills B6 group])
(;B[ra]CR[ra]
;W[an]CR[an]C[B6 group is worth much more than T18 group])
(;B[bb]CR[bb]
;W[an]CR[an]C[L group is dead - so after playing B18 black needs one more move to live in the corner - in that time white can finish off B6 and L17 groups])
(;B[ca]CR[ca]
;W[an]CR[an]C[L group is dead - so after playing B18 black needs one more move to live in the corner - in that time white can finish off B6 and L17 groups])
(;B[ba]CR[ba]
;W[an]CR[an]C[L group is dead - so after playing B18 black needs one more move to live in the corner - in that time white can finish off B6 and L17 groups])
(;B[an]CR[an]
;W[ah]CR[ah]
;B[ai]CR[ai]
;W[ka]CR[ka]
(;B[ra]CR[ra]C[RIGHT])
(;B[sq]CR[sq]
;W[ra]CR[ra])
(;B[rr]CR[rr]
;W[ra]CR[ra])
(;B[sr]CR[sr]
;W[ra]CR[ra])
(;B[bb]CR[bb]
;W[ra]CR[ra])
(;B[ca]CR[ca]
;W[ra]CR[ra])
(;B[ba]CR[ba]
;W[ra]CR[ra])
(;B[gr]CR[gr]
;W[ra]CR[ra])
(;B[gs]CR[gs]
;W[ra]CR[ra])
(;B[ak]CR[ak]
;W[ra]CR[ra])
(;B[al]CR[al]
;W[ra]CR[ra]))
(;B[ka]CR[ka]
;W[an]CR[an]C[B6 group is worth more than L17 group])
(;B[ah]CR[ah]C[Wrong - A6 has bigger endgame value than A12]))