User blog comment:Edwin Shade/Questions About Madore's Psi Function/@comment-80.98.179.160-20180124154752/@comment-34434829-20180124163511

Answer 1 is correct.

2 is wrong on so many levels that I wouldn't know where to start to correct it.

3 is actually okay, even if incomplete.

4 sounds like the punchline of a joke about the correct-yet-completely-useless answers that mathematicians are famous for: "Me: Do you know what time it is? Mathematician: Yes."