Cool Envelopes

Probability Level 1

There are 3 envelopes, one with $1, another with$2, and the other with \$4. You do not know which envelope has which amount of money.

After you pick one at random, you are told which envelope of the remaining 2 has the lowest value, but not the actual value of that envelope. What is the expected value if you switch to the last envelope remaining (the one that has not yet been mentioned)?

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