I am trying to write a query that will provide the average of 5 columns. Here is my query, but each time I try to run it I get this error:

You tried to execute a query that does not include the specified expression 'Proposal #' as part of aggregate.

Average Rating: Avg([Eval #1 Overall Rating]+[Eval #2 Overall]+[Eval #3 Overall]+[Eval #4 Overall]+[Eval #5 Overall])

My fields are:
proposal #
...