Using a calculated column later in the query

SELECT
  CASE 
    WHEN Volumes > 0 AND Volumes <= 100 THEN 7.6
    WHEN Volumes > 100 AND Volumes <= 500 THEN 8.6
    WHEN Volumes > 500 THEN 9.0
  END AS Rate,
  Volumes
  --need a [Rate] * [Volumes] AS [Total] type of column here.
FROM 
  Transactions
WHERE 
  ID = @ID