SYSTEM FOR DETERMINING AVAILABILITY OF TRADABLE INSTRUMENT

PROBLEM TO BE SOLVED: To provide a technique for executing a spread efficiently and advantageously.SOLUTION: A trading system comprises a trading platform and a plurality of interfaces. The trading platform executes sale orders and purchase orders. The interfaces transmit the sale orders and the purchase orders to the trading platform. At least one interface also determines an available offered quantity of a first instrument that represents an amount of the first instrument currently available to be purchased. The interface also determines an unavailable offered quantity of the first instrument that represents an amount of the first instrument specified by a sale order associated with a first transaction. The interface also determines a bid quantity specified by a purchase order associated with the first transaction and calculates a temporarily unavailable offered quantity of the first instrument on the basis of a difference between the unavailable offered quantity of the first instrument and the bid quantity. Additionally, the interface calculates a quantity of a second instrument on the basis of a sum of the available offered quantity of the first instrument and at least a portion of the temporarily unavailable offered quantity.