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The estimated times and immediate predecessors for the activities in a project at Howard Umrah's retinal scanning company are given in the following table. Assume that the activity times are independent.

$\backslash$table$[[$Activity$,$Time $($weeks$),\backslash$table$[[$Immediate$],[$Predecessor$($s$)]],$Activity,Time $($weeks$),\backslash$table$[[$Immediate$],[$Predecessor$($s$)]]],[a,m,$b$,a,m,$b$],[\frac{?}{\text{b}\text{a}\text{r}}(A),\frac{?}{\text{b}\text{a}\text{r}}(8),10,13,,\frac{?}{\text{b}\text{a}\text{r}}(C),7,10,12,\frac{?}{\text{b}\text{a}\text{r}}(A)$