DAX Query for Top Manufacturer by Salesperson

This query is working except that I only want the top record.  I've used MAX and TopN a few different ways without any luck.  It's based off the 43,213.00 in column 'a'.  So basically it's the top manufacturer for each outside sales name.  Currently I'm getting ALL the manufacturers for each outside sales person.

Thanks in advance for any suggestions.......  Terry

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Table = SUMMARIZE('Top 10 Branches','Top 10 Branches'[Outside Sales.Outside Sales Name], 'Top 10 Branches'[Time.Date].[Date],'Top 10 Branches'[Parts.Parent Manufacturer], "a",SUM('Top 10 Branches'[Book Resale - SALE]))