Can someone please help me with Part E? *DETAILED explanation appreciated.

The Action Toy Company has decided to manufacture a new train set, the production of which is broken into six steps. The demand for the train is 4,500 units per 40 -hour workweek: \begin{tabular}{ccc} \hline Task & \begin{tabular}{c} Performance Time \\ (seconds) \end{tabular} & Predecessors \\ \hline A & 20 & - \\ B & 30 & A \\ C & 14 & A \\ D & 14 & A \\ E & 12 & B, C \\ F & 27 & D, E \\ \hline \end{tabular} e) The total idle time per cycle for the process = seconds (enter your response as a whole number)