First you must find out the clause of the quality problems and furnish sufficient evidence.
首先你的查查有关质量问题的条款,并提供足够的证据。
They've promised to keep both we quality and the quantity of the 300 bicycles in conformity with the contract stipulations.
他们已承诺那300辆自行车的质量和数量一定与合同规定相吻合。