Please crash the network

Activity Information:

Activity Predecessors Duration Crash Duration Crash Cost$/$Unit

A $-21800$

B $-32500$

C $-42400$

D A $74500$

E B$,$ D$,$ C $63900$

F B$,$ C $53100$

G D$,$ E $97200$

H F $84150$

I G$,$ H $10800$