用所给动词的适当形式填空。

1.  Don't forget ______ (turn) off the lights after school.

2.  She would rather    ____ (learn) French than Japanese.

3.  The old man is too old   ___ _ (walk).

4.  Not______ (get) enough sleep has serious effects on our brain's ability to work.

5.  His father didn't allow him ______ (watch) TV on weekends.

某大型工程由于工期要求紧，在初步设计完成后，通过招标，某施工单位中标，在施工图刚出一半时，便开始施工，由于工程技术难度大，所以在施工中发生了设计变更等不可预料的事件，导致承包商的索赔增加，项目监理机构对索赔进行了管理。
问题

项目监理机构处理费用索赔的依据是什么