给我解释一下做这道题---**Diagram Description:** * **Type:** Network diagram, representing a project schedule. This appears to be a Critical Path Method (CPM) or PERT chart. * **Main Elements:** The diagram consists of several nodes (boxes) representing tasks and directed edges (arrows) representing dependencies between tasks. * **Task Nodes:** Each task is represented by a box divided into sections. The sections are labeled: * Top Left: ES (Early Start) * Top Right: EF (Early Finish) * Bottom Left: LS (Late Start) * Bottom Right: LF (Late Finish) * Center: Duration and Task Name. * **Tasks and Durations:** * Task A: Duration = 4 * Task B: Duration = 6 * Task C: Duration = 7 * Task D: Duration = 5 * Task E: Duration = 8 * Task F: Duration = 8 * Task G: Duration = 3 * **Dependencies (Arrows):** * An implicit start node connects to Task A. * Task A connects to Task B and Task E. * Task B connects to Task C. * Task C connects to Task D. * Task D connects to Task G. * Task E connects to Task F. * Task F connects to Task G. * **Given Values in Diagram:** * Task A has an initial ES value of 0. **Questions:** 1. 确定所有任务的ES, EF, LS, LF * *English Translation:* Determine the ES, EF, LS, and LF for all tasks. 2. 确定关键路径以及关键路径的长度? * *English Translation:* Determine the critical path and the length of the critical path? 3. 确定F的自由浮动和总浮动? * *English Translation:* Determine the free float and total float for F?