Manufacturing statements and cost behavior

Tampa Foundry began operations during the current year, manufacturing various products for industrial use. One such product is light-gauge aluminum, which the company sells for $36 per roll. Cost information for the year just ended follows.


Per Unit Variable Cost Fixed Cost
Direct materials $4.50 $ —
Direct labor 6.5 —
Factory overhead 9 50,000
Selling — 70,000
Administrative — 135,000



Production and sales totaled 20,000 rolls and 17,000 rolls, respectively There is no work in process. Tampa carries its finished goods inventory at the average unit cost of production.
Instructions:

Determine the cost of the finished goods inventory of light-gauge aluminum.

Can someone please, step by step go through the process.

The following I have tried but I don't know which is correct and why?
1) 20,000-17,000=3,000
3,000x36=108,000 (cost of the finished goods inventory)

2) 20,000x36=720,000
720,000+3,000=723,000 (cost of the finished goods inventory)

Per Unit Variable Cost Fixed Cost
Direct materials $4.50 $ —
Direct labor 6.5 —
Factory overhead 9 50,000
Production and sales totaled 20,000 rolls and 17,000 rolls, respectively There is no work in process. Tampa carries its finished goods inventory at the average unit cost of production.
Instructions:

Determine the cost of the finished goods inventory of light-gauge aluminum.

Cost of finished goods inventory:
Variable
Direct materials $4.50
Direct labor 6.5
Factory overhead 9
Total variable $20
Fixed
50,000/20,000 = $2.50
Total unit costs 22.50
Inventory Valuation
3,000 x $22.50 = $67,000

In your answer you were using selling price of $36 instead of cost of production

How did you find the total unit cost?