某施工单位承揽了一项综合办公楼的总承包工程，在施工过程中发生了如下事件：事件1：施工单位与某材料供应商所签订的材料供应合同中未明确材料的供应时间。急需材料时，施工单位要求材料供应商马上将所需材料运抵施工现场，遭到材料供应商的拒绝，两天后才将材料运到施工现场。事件2：某设备供应商由于进行设备调试，超过合同约定的期限交付施工单位订购的设备，恰好此时该设备的价格下降，施工单位按下降后的价格支付给设备供应商，设备供应商要求以原价执行，双方产生争执。事件3：施工单位与某施工机械租赁公司签订的租赁合同约定的期限已到，施工单位将租赁的机械交还租赁公司并交付租赁费，此时，双方签订的合同终止。事件4：该施工单位与某分包单位所签订的合同中明确规定要降低分包工程的质量，从而减少分包单位的合同价格，为施工单位创造更高的利润。

在什么情况下导致合同无效？

Nofunds Company is in severe financial difficulty. It has lost a major customer and its cash flows have diminished to the extent that the company cannot pay its financial obligations as they fall due. The company owes 75 million dong in unpaid wages to its employees, 150 million dong to the bank on an unsecured overdraft, 300 million dong on a mortgage secured on its business premises and 200 million dong to unsecured creditors. The general director of the company repaid a debt of 600 million dong due to a bank, this borrowing being supported by his personal guarantee.The total assets of the company are estimated to be 500 million dong.Required:

(b) Explain the order in which payments would be made by the liquidator under the provisions of the Law on Bankruptcy. (5 marks)