(;AB[ab]AB[bc]AB[cb]AB[ba]AW[ae]AW[be]AW[bd]AW[cd]AW[cc]AW[dc]AW[db]AW[eb]AW[ea]AP[goproblems]
(;W[ac];B[ad]MA[ac]
(;W[ca];B[da]C[]MA[ca]
(;W[ac]C[Double Ko, black cannot win them bothRIGHT])
(;W[ca]C[NOTTHIS]))
(;W[da];B[ca]C[Ko is not best])
(;W[ac]C[NOTTHIS]))
(;W[ca];B[da]MA[ca]
(;W[ac];B[ad]MA[ac]
(;W[ca]C[RIGHT])
(;W[ac]C[NOTTHIS]))
(;W[ad];B[ac]C[Ko is not best])
(;W[ca]C[NOTTHIS]))
(;W[ad];B[ac]
(;W[ca];B[da]C[Ko is not best])
(;W[da];B[ca]C[Black is alive]))
(;W[da];B[ca]
(;W[ac];B[ad]C[Ko is not best])
(;W[ad];B[ac]C[Black is alive])))