SELECT  DAY(nt.DateOfOrder) AS [Day],
        FORMAT(AVG(nt.SumPerOrder), 'N2') AS TotalProfit
FROM
(SELECT oi.Quantity,
       (i.Price * oi.Quantity) AS SumPerOrder,
       CAST(o.DateTime AS DATE) AS DateOfOrder
FROM Orders AS o
JOIN OrderItems AS oi
ON oi.OrderId = o.Id
JOIN Items AS i
ON i.Id = oi.ItemId) AS nt
GROUP BY nt.DateOfOrder
ORDER BY nt.DateOfOrder