I'm not sure why koni is used here over scii. In Spanish and French, saber and savoir, respectively, would be used.
Koni is to know a person or thing (the answer) while scii is to know something is or was happening
In the notes they've said that 'scii' is for facts and knowledge. Isn't this a case of facts and knowledge?
Oh. I thought "koni" was to know people, and "scii" was to know things. Woops.
Koni is used for things that you know from personal experience, so presumably the answer is something non-intellectual in nature.
I think that maybe because the sentence is talking about knowing something specific as the answer, koni is used. Just my explanation though
In the English-language Wiktionary, the example sentence is 'Mi ne scias la respondon'. So apparently scii and koni are both acceptable here.