Calculate work busines days for rolling getdate days -90

I need to get a count of business days for the last rolling 90 days.
I.e  i nee to calculate how many average calls a service rep has made per business days.

The sp belowis what i have now. I need to see one row per representative with the record count for that rep and the average call per day based on the amount of calls /Business days.
Hope this makes sense.

Thank you

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:		Anthony Cardullo
-- Create date: 07/15/09
-- Description:	Calculate Average Per day call completion per rep for last 90 days
-- EXEC[dbo].[usp.AverageCallPerdayPerRep90Days]
-- =============================================
ALTER PROCEDURE [dbo].[usp.AverageCallPerdayPerRep90Days]
	
	
AS
BEGIN
	-- SET NOCOUNT ON added to prevent extra result sets from
	-- interfering with SELECT statements.
	SET ROWCOUNT 0
	SET NOCOUNT ON;
 
    -- Insert statements for procedure here
	SELECT DISTINCT 
                      dbo.root_SERIAL_EQUIP.PROGRAM_TYPE, dbo.root_SERIAL_EQUIP.INSTALL_DATE_SEQ, dbo.root_SERV_CALL.CALL_ID, 
                      dbo.root_SERV_CALL.CALL_STATUS_SCA, dbo.root_SERV_CALL.CALL_TYPE, dbo.root_SERV_CALL.SYMPTOM_CODE, 
                      dbo.root_SERV_CALL.OPEN_DATE_SCA, dbo.root_SERV_CALL.MODEL, dbo.root_SERV_CALL.SERIAL, dbo.root_SERIAL_EQUIP.VENDOR, 
                      dbo.root_SERV_CALL.REPRESENTATIVE, dbo.root_SERV_CALL.COMPLETE_DATE_SCA
FROM         dbo.root_SERV_CALL INNER JOIN
                      dbo.root_SERIAL_EQUIP ON dbo.root_SERV_CALL.MODEL = dbo.root_SERIAL_EQUIP.MODEL AND 
                      dbo.root_SERV_CALL.SERIAL = dbo.root_SERIAL_EQUIP.SERIAL
WHERE     (dbo.root_SERV_CALL.OPEN_DATE_SCA > DATEADD(day, - 90, GETDATE()))
END

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