Homework

$\backslash$table$[[$Activity$,$Description,Predecessors,Duration$],[$A$,$Site cleaning,$---,4],[$B$,$Removal of trees,$---,3],[$C$,$General excavation,A$,8],[$D$,$Grading general area,B$,$C$,7],[$E$,$Excavation for trenches,B$,$C$,12],[$F$,\backslash$table$[[$Placing formwork and reinforcement$],[$for concrete$]],$D$,$E$,2],[$G$,$Installing sewer lines,F$,$G$,5],[$H$,$Installing other utilities,,$6]]$

$(1)$ Draw project network diagrams based on the logical relationships in the table.

$(2)$ Calculate the time parameter, determine the time of the project and the Critical Path.