(;AB[ab]AB[ac]AB[bc]AW[aa]AW[bb]AW[ca]AW[db]AW[cc]AW[cd]AB[dc]AB[ec]AB[eb]AB[de]AB[ee]AB[cf]AB[bf]AP[goproblems]
(;B[ae];W[be]
(;B[ad]C[RIGHT])
(;B[ba]C[Involves a ko! There is another solutionRIGHT]))
(;B[be];W[bd];B[ba];W[ad];B[cb]C[Adv. koCHOICE])
(;B[ad];W[ae];B[ba];W[bd]C[Adv. koCHOICE])
(;B[ba];W[bd];B[cb]C[Adv. koCHOICE]))