Use the Table the Supply Schedule for Beaded Necklaces

Use the table The Supply Schedule for Beaded Necklaces. What can be inferred about Oliver when the price of necklaces is $20?
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A) His opportunity cost of producing a fourth necklace is higher than $20.
B) His total costs of production are higher than $20.
C) His cost of producing a typical necklace when he produced four necklaces is higher than $20.
D) He has a net gain of producing a fourth necklace when the price is $20.