合同可以变更，但是当事人对合同变更的内容约定不明确的，推定为(26)。

(62)

(63)

(64)

A project management technique that is currently in widespread use is the(71) . The purpose of this technique is to detail, in hierarchical fashion, all of the activities that are required to meet project objectives. There are some special activities called(72) , which are events that signify the accomplishment or completion of major deliverables during the project. Most system development methodologies also provide(73), whose purpose is to contain the various pieces of relevant information-feasibility assessments, schedules, needs analysis, and so forth-in a single place so that they can be presented to project clients and other related parties. Several types of important network diagrams are used in project management.(74) was developed to make clear the interdependence between project tasks before those tasks are scheduled.(75) offers the advantage of clearly showing overlapping tasks.

(61)

(59)

某省6个城中(A～F)之间的网络通信线路(每条通信线路旁标注厂其长度公里数)如图1-4所示。

 如果要将部分千兆通信线路改造成万兆通信线路，以提升各个城市网络之间的通信容量，则至少要改造总计(61)公里的通信线路，这种总公里数最少的改造方案共有(62)个。

(57)

制造某种产品需要4道工序，每道工序可选用多种方法。图5—3列出了制造这种产品各道工序可选用的不同方法：从节点1开始，连续经过4条线段(表示4道工序所选用的方法)组成一条线路，直到节点 12结束。每条线段上标记的数字表示利用相应方法每件产品可以获得的利润(元)。企业为了获取最大利润，需要找出从节点1～节点12的一条线路，使其对应的各道工序的利润之和最大。

利用运筹方法计算后可知，制造每件产品可以获得的最大利润是(70)元。

某工程程包括A、B、C、D、E、F、G、H、I 9个作业，各个作业的紧前作业、所需时间、所需人数如表1-1所示(假设每个人均能承担各个作业)。

 该工程的计算工期为(59)月。按此工期，整个工程至少需要(60)人。