$4.$ A cheese processing plant has several tasks that need to be done as listed in the following table with time for each activity and precedence relationships. The line works $5$ days a week, for $8$ hours each day. The plant provides cheese to several supermarket chains at a rate of $600$ lbs per week.

Activity Predecessor Time $($minutes$)$ Workstation A

$-$ B

C D E F

G H I

$-$

A A

B$,$ C B

C

D$,$ E D$,$ F

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