the calculation of percentage of cost is unclear please explain that only

At a lump-sum cost of $69,000, Pratt Company recently purchased the following items for resale Item No. of Items Purchased 4,000 2,000 6,000 Resale Price Per Unit $3.75 12.00 6.00 The appropriate cost per unit of inventory is: $3.75 $12.00 $6.00 $3.38 $10.80 $5.40 $3.45 $11.04$5.52 $5.75 $5.75 $5.75 please show solution and how you come up with percentages