Given the Following Line Balance Data For Eight Hours of Operating Time Per Day and a c

Given the following line balance data: $$\begin{array} { l c c } \text { Task } & \text { Predecessor } & \text { Time (seconds) } \\\hline \mathrm { t } & \text { none } & 15 \\\mathrm { u } & \mathrm { t } & 14 \\\mathrm { v } & \mathrm { t } & 7 \\\mathrm { w } & \mathrm { u } & 6 \\\mathrm { x } & \mathrm { v } & 8 \\\mathrm { y } & \mathrm { w } , \mathrm { x } & 10 \\\mathrm { z } & \mathrm { y } & 21\end{array}$$ For eight hours of operating time per day and a desired output rate of 960 units per day, what is the percentage of idle time for the balance which uses the minimum number of stations?