#feedback I think it would be helpful to have some more medium-level questions to help get our feet under us before throwing us into the deep end with these extremely hard ones. I want more practice and to gain more understanding before taking on something more difficult. It's getting more and more discouraging getting all these level 5s wrong.

I fully agree that a separate video in on this would be helpful. I don't fully understand this point either, especially in the previous lesson.

But I think this lesson made it a bit more clear for me. The rule/conclusion we're trying to reach is the use of the computer is justified. In order to make that conclusion, justified must be the necessary condition because this is what has to happen/must be true. It cannot be in the sufficient condition. Therefore,

The contrapositive of justified → comp tob works, because "not justified" will be the necessary condition. This is the conclusion and the outcome of the rule we are trying to reach.

The contrapositive of comp tob and rgbel → justified does not work, because "not justified" will be the sufficient condition and not the conclusion.

I think this is the right take, but I'm still not fully clear on this.

#feedback. I'm confused about why you can't contrapose here.

Is this not correct?

could play a practical joke → /contempt and /b(significant harm)

#feedback I don't think it was emphasized enough in the previous lessons that the "Two Split Mosts" rule also applies to two "all" or "must" arrows. These two Skill Builders use this rule a lot, and I think it's tripping people up. I know I was confused at how you could get all these some relationships. This is how I see it:

For example:

A ‑m→ B

A ‑m→ C

You can validly conclude that B ←s→ C ("Two Split Mosts")

But you can also do this:

A → B

A → C

You can validly conclude that B ←s→ C (Because "All" or "Must" arrows are even stronger than "Most" arrows, 1 or more Bs must be Cs, and vice versa.)

You can also use the contrapositive with this rule:

B → A contrapositive /A → /B

C → A contrapositive /A → /C

You can validly conclude that /B ←s→ /C

A rule of thumb is that the sufficient conditions must be the same in both relationships to validly infer a some relationship between the necessary conditions. If the necessary conditions are the same, you cannot infer a some relationship. You must take the contrapositive.