Need well defined and structured answer to all parts with detailed explanation to all steps

A farm implements dealer is seeking a fourth warehouse location to complement three existing warehouses. There are three potential locations: Charlotte, Atlanta \& Columbia. Charlotte would involve a fixed cost of $4000 per month and a variable cost of $4 per unit; Atlanta would involve a fixed cost of $3500 per month and a variable cost of $5 per unit \& Columbia would involve a fixed cost of $5000 per month and a variable cost of $6 per unit. Use of Charlotte location would increase system transport cost by $19000 per month, Atlanta by $22000 per month and Columbia by $18000 per month. Which location would result in the lowest total cost to handle 800 units per month