Anthony Office Supplies Sells Refills on Printer Ink Cartridges for $16

Anthony Office Supplies sells Refills on printer ink cartridges for $16 per refill.Variable costs are $4 per refill.Fixed costs are $2,000 per month.What is the contribution margin per refill?

A) $ 1.33
B) $ 0.75
C) $12.00
D) $ 4.00