The graph shows the cost curves of an individual firm in a perfectly (or purely) competitive industry. Use the line labeled Supply to trace out the firm's short-run supply curve.20 Supply 19 Marginal cost 18 A B C D 17 16 Average total cost 15 Average variable cost Price ($) 6 9 12 15 18 21 24 27 30 33 36 39 QuantityWhat is the minimum quantity this firm will produce in the short run? O 12 units 3 units O 18 units 6 units In the long run, the firm will shut down if the market price stays below O $2 O $6 O $12 O $9