When X is offered, Y or Z are offered or BOTH

[abajaj]

I have two question regarding rules that are phrased "when X is offered, Y or Z are offered or BOTH". First, is this the right way to diagram them?

x Y + Z

Next, How do you make a contrapositive for something like this?

Thanks!

[Dave Killoran]

That diagram goes just a bit too far by using "+" because "+" implies that you have to have both. Instead, the rule indicates that " Y or Z are offered," so you would want to use "or" instead:

X Y or Z

Remember, "or" automatically allows for both unless otherwise specified, so once you have "or," you already know that both are possible (they just state it here for emphasis).

Please let me know if that helps. Thanks!

[abajaj]

Yes, that makes sense. But the contrapositive for that would no Y + no Z no X which isn't true because there can still be an X without both present. So can we just assume that there is always going to be either a Y or a Z in the game? But is that the most we can do with it for now?

[Dave Killoran]

Sorry--I missed your question about the contrapositive!

Actually, the diagram you have for the CP is correct. Think about it for a sec--if you have X, you have to have either Y or Z. So what happens if you have neither? That's right, no way you can have X.

Please let me know if that makes sense. Thanks!