A party exercising its choice shall notify the other party in a timely manner, and when the notice is received by the other party, the subject matter is determined. The subject matter so determined may not be modified, except with the consent of the other party. 当事人行使选择权应当及时通知对方，通知到达对方时，标的确定。标的确定后不得变更，但是经对方同意的除外。 If price or remuneration is not clear,performance shall be in accordance with the prevailing market price at the place of performance at the time the contract was concluded, and if adoption of a price set by the government or based on government issued pricing guidelines is required by law, such requirement applies. 价款或者报酬不明确的，按照订立合同时履行地的市场价格履行；依法应当执行政府定价或者政府指导价的，依照规定履行。