So do PERT$)$ The documents of a project are given as follows: $1.$ Calculate the expected time and variance for each job. Time $($week$)$ Trinh tu No $2.$ Draw the comparison by PERT. $($Predecesor$)$ b m $3.$ If it takes $28$ weeks to complete the project, what $\%$ of the project can be completed?$1.$ T$$nh thoi gian k$$ vong v$$ ph$$ong sai c$$a t$$ng c$$ng vi$$c$.$ Thoi gian $($tu$$n$)$ Trinh tu STT $2.$ V$$ so do PERT. $($Ng$$i ti$$n nhi$$m$)$ b t$$i $3.$ N$$u y$$u c$$u trong $28$ tuan phai ho$$n th$$nh du $$n thl kh$$ nang dat duoc l$$ bao nhi$$u $\%?$