Trade: 30 contracts at $0.53 (Carol's resting price). Carol is partially filled. - Carol's remaining: 50 - 30 = 20 contracts at $0.53. - Dave's order is fully filled. - Book: Bids = [{Carol, $0.53, 20}, {Alice, $0.50, 100}], Asks = [{Bob, $0.55, 80}]