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Consider the widget exchange. Suppose that each widget contract has a market value of $0 and a notional value of $100. There are three traders, A, B, and C. Over one day, the following trades occur: A long, B short, 5 contracts. A long, C short, 15 contracts. B long, C short, 10 contracts. C long, A short, 20 contracts. What is trader B's net position in the contract at the end of the day?