thanks to chrise, tails and karmaGfa for their help!
(;AB[db]AB[dc]AB[de]AB[ca]AB[bb]AB[be]AB[af]AB[bf]AB[cf]AB[bg]AW[cb]AW[cc]AW[cd]AW[ce]AB[dd]AW[bd]AW[ad]AW[df]AW[dg]AW[ch]AW[bh]C[white's best result]MA[be]MA[bf]MA[af]MA[bg]MA[cf]AP[goproblems]
(;W[ae];B[ac])
(;W[cg];B[ac]
(;W[ah];B[bc])
(;W[ag];B[ah];W[ai];B[bc];W[ag];B[ae]))
(;W[ah];B[ac];W[cg];B[bc])
(;W[bc];B[ae])
(;W[ac];B[ba]
(;W[cg];B[ab];W[ah];B[bc])
(;W[aa];B[ab]
(;W[cg];B[bc])
(;W[bc];B[ae]))
(;W[ab];B[bc]
(;W[cg];B[da];W[ah];B[aa])
(;W[aa];B[ae]))
(;W[bc];B[ab]))
(;W[ab];B[ba]
(;W[bc];B[ae])
(;W[ac];B[da];W[cg];B[aa];W[ah];B[bc])
(;W[cg];B[bc]
(;W[ag];B[ah];W[ai];B[ac])
(;W[ah];B[ac])
(;W[ac];B[da]
(;W[ag];B[ah];W[ai];B[aa];W[ag];B[ae])
(;W[ah];B[aa]))))
(;W[ba];B[aa]
(;W[bc];B[ae])
(;W[ac];B[ab]
(;W[cg];B[ah];W[ai];B[bi];W[ag]C[black played a direct-ko. Of course, it can mean a lot of ko-threats given to white while escaping on the border, but finally the result will be good for black because it gives influence RIGHT])
(;W[ah];B[ae]
(;W[cg];B[bc])
(;W[ag];B[bc])))
(;W[ah];B[ac]
(;W[ag];B[bc])
(;W[cg];B[bc])
(;W[bc];B[ae]))
(;W[cg];B[ac];W[ah];B[bc])))