ControlThree critical path activities are candidates for crashing on a CPM network. Activity details are in the table below.

Activity NT CT CC NC Predecessor

A $7$ days $5$ days $$9000$ $$7000$

B $8$ days $6$ days $$8000$ $$6000$

C $3$ days $2$ days $$2400$ $$1800$ A

D $12$ days $9$ days $$7700$ $$5000$ B

a$.$ What is the project length?

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b$.$ What is the critical path?

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c$.$ To reduce the project by one day, which activity would be crashed and how much would it cost$?$

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d$.$ If we wanted to crash the project by an additional day, which activity would be crashed and how much would the total cost be for the two days?