A simple problem, but the solution is still interesting
(;SZ[19]AW[pn]AW[rn]AW[po]AW[ro]AW[np]AW[op]AW[nq]AW[pq]AW[qq]AW[pr]AW[rr]AW[ps]AB[pp]AB[qp]AB[rp]AB[oq]AB[rq]AB[or]AB[os]C[Black to play]GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]RU[Japanese]KM[0.00]TM[]PW[Weiß]PB[Schwarz]
(;B[rs];W[nr]
(;B[qr];W[ns];B[sr];W[qs];B[sp]C[Now black can fight a ko RIGHT])
(;B[sr];W[ns];B[qr];W[qs];B[sp]C[Now black can fight a ko RIGHT]))
(;B[qs];W[qr];B[sr];W[rs]C[This is wrong: black can't play T1 and loses all his stones])
(;B[sr];W[rs];B[qr];W[qs]C[Black can't play T1, so he is dead];B[sq];W[nr]C[White wins the capturing race])
(;B[qr];W[qs];B[sr];W[rs];B[sq];W[nr]C[White wins the capturing race]))