How do you calculate variable unit costs and total annual costs?

Annual units sold, 1000. Raw materials annual cost 650. Building rent annual cost 9000. If sales volume increased to 6000 units and 8000 units, what is the total annual cost and unit cost for fixed variable?

Cost per unit of raw material=650/1000= 0.65

Fixed cost (Rent) =9000

Fixed cost per unit= 9000/1000= 9.00

If the sales volume increases to 6000 units, then total cost= 12900 and cost per unit = 2.150

Variable cost+ fixed cost= (0.65*6000) + 9000= 12900 / 6000= 2.15

If the sales volume increases to 8000 units, then total cost= 14200 and cost per unit = 1.775

(0.65*8000) + 9000= 14200 / 8000 = 1.775