This problem is nothing special, but for some reason I like the fact that THIS starting position leads to THAT final position :)
Please find the best result for White!
(japanese rules)
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[4]KM[0.00]
PW[Weiß]PB[Schwarz]AW[db][cc]AB[bb][ad][bd][cd]C[White to play - what's the best he can do?]PL[W]
(;W[bc]CR[bc]
;B[ac]CR[ac]
(;W[ab]CR[ab]
;B[aa]CR[aa]
(;W[dd]CR[dd]
(;B[cb]CR[cb]C[Taking the ko is worse (see variations)]
;W[ab]CR[ab]
;B[ac]CR[ac]
(;W[bd]CR[bd]
;B[ca]CR[ca]C[Seki! White wins by 2 points (4 prisoners against 2) RIGHT])
(;W[ca]CR[ca]
;B[bd]CR[bd]C[Seki! White wins by 2 points (4 prisoners against 2) RIGHT]))
(;B[dc]CR[dc]
;W[cb]CR[cb]
;B[ca]CR[ca]
;W[dd]CR[dd]C[Black is completely lost]))
(;W[cb]CR[cb]
;B[ca]CR[ca]C[It's to late to start the ko now - Black wins by one point (the prisoner)])
(;W[ca]CR[ca]
;B[cb]CR[cb]
;W[dc]CR[dc]C[Black wins by one point (the prisoner)]))
(;W[cb]CR[cb]
;B[ca]CR[ca]C[White can't start the ko anymore and will lose by one point (he has to sacrifice a stone to prevent a black eye)])
(;W[ca]CR[ca]
(;B[ba]CR[ba]
;W[ab]CR[ab]
;B[aa]CR[aa]
;W[cb]CR[cb]C[B4??! Stupid Black :) Instead of this big mistake, he should have played B C3 (see variations).])
(;B[cb]CR[cb]
;W[dc]CR[dc]
(;B[ba]CR[ba]
;W[ab]CR[ab]C[B4??! Stupid, stupid Black :) Of course, if Black plays c3 himself instead, it's a seki (see variations)])
(;B[ab]CR[ab]
;W[ba]CR[ba]C[Seki & jigo!])))
(;W[dd]CR[dd]
(;B[ab]CR[ab]
;W[cb]CR[cb]
;B[ca]CR[ca]
;W[ba]CR[ba]
;B[dc]CR[dc]C[Black wins!])
(;B[dc]CR[dc]
;W[cb]CR[cb]
;B[ca]CR[ca]
;W[dd]CR[dd]
;B[ab]CR[ab]
;W[ba]CR[ba]
;B[dc]CR[dc]C[Black wins!])))
(;W[cb]CR[cb]
;B[bc]CR[bc]
;W[ba]CR[ba]
(;B[ab]CR[ab]
;W[ca]CR[ca]C[Seki & Jigo, but both can do better!])
(;B[ca]CR[ca]
;W[da]CR[da]
;B[ab]CR[ab]C[White is lost - 'one eye beats no eye'!]))
(;W[ca]CR[ca]
;B[bc]CR[bc]
(;W[cb]CR[cb]
;B[ba]CR[ba]
;W[ab]CR[ab]
;B[dd]CR[dd]
;W[ac]CR[ac]
;B[aa]CR[aa]
;W[ab]CR[ab]
;B[ac]CR[ac]C[Maybe Black can also play d2 instead of d1, but as usual I am not sure about the rules :) Anyway, this is a three point win for black.])
(;W[ba]CR[ba]
;B[cb]CR[cb]
;W[dc]CR[dc]
;B[ab]CR[ab]C[Black wins!])))