The duration and resource usage for each activity are showed in the table below.

Activity Predecessor Total Processing Time (days) # of painters required/day A --- 0.5 2 B A 1 2 C B 1 1 D B 1 2

How many painter-days are required for the whole project?

\begin{tabular}{|c|c|c|c|} \hline Activity & Predecessor & \begin{tabular}{l} Total \\ Processing \\ Time \\ (days) \end{tabular} & \begin{tabular}{l} \# of painters \\ required/day \end{tabular} \\ \hline A & --- & 0.5 & 2 \\ \hline B & A & 1 & 2 \\ \hline C & B & 1 & 1 \\ \hline D & B & 1 & 2 \\ \hline \end{tabular}