User Email Address

I have a form with a user field.  It allows a person to enter a form, but select another user as the owner in a field called "PRM".  For example, User 1 enters the form, but selects User 2 as the "PRM" owner.

How can I create a field using a formula for User 2's email address?

I know the formula below, but this would only bring in the email address of User 1 in this case.
UserToEmail(User())

Thank you!

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Val Wong
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