GoEye: Defender's answer not strongest one for solution - he needs to make atari from another side and make ko shape. Is this really not a Ko, if E17-E18-F17-C18 sequence?
posetcay: Attacker captures E16 group in sente, this is not a good result for the defender.
Thibaut PERRIN: Please check this: another solution exist without a KO. One of the branch comes to a good result.
I believe that this problem is 70 XP because of an error in the Tsumego.
d4rkm4tter: Ko is considered incorrect in this problem. If there is another correct sequence, please show.
Defender's answer not strongest one for solution - he needs to make atari from another side and make ko shape. Is this really not a Ko, if E17-E18-F17-C18 sequence?