$4.$ For a network shown below, normal time, crash time, normal cost, crash cost are given in table. Contract the network by crashing it to optimum value and calculate optimum project cost. Indirect cost Rs $100/-$ per day.

Normal

Crash

Activity

Time in days

Cost in Rs

Time in days

Cost in Rs

$1-2$

$3$

$300$

$2$

$400$

$2-3$

$6$

$480$

$4$

$520$

$2-4$

$7$

$2100$

$5$

$2500$

$2-5$

$8$

$400$

$6$

$600$

$3-4$

$4$

$320$

$3$

$360$

$4-5$

$5$

$500$

$4$

$520$