I was (again) thinking about what you are trying to proof.
Then I start to realize that our mailman, who delivers me many envelopes and packages each week doesn't know there are coins inside.
If and only if, the envelope survives, he will know it at the time he delivers me the envelope
Bad choice.
Then I start to realize that our mailman, who delivers me many envelopes and packages each week doesn't know there are coins inside.
If and only if, the envelope survives, he will know it at the time he delivers me the envelope
Bad choice.