Question

A project has activities A, B, C and D as shown below

Activity	Normal (days)	Cost Slope (Rs/day)
A (1-2)	6	300
B (1-3)	8	100
C (2-3)	3	200
D (3-4)	4	500

The normal cost of the project is Rs. 4000 and the project overhead cost is Rs. 300 per day. If the project duration has to be crashed to 10 days the total project cost would be _______

• A. 7500
• B. 7500
• C. 8000
• D. 7900

Answer 1

The correct option is D 7900

Activity	Cost Slope
A	300
C	200
D	500

Crash 'C' by 1 day in stage 1
Stage 1:
Path Duration
A-C-D 12
B-D 12

Target is 10 days, hence we need to crash both the critical paths by 2 days

'A' by 1 day
'B' by 1 day
A-C-D path becomes 10 days

Path Duration
A-C-D 10
B-D 10

'B' by 2 days $\Rightarrow$ B - D

Total project cost for 10 days = Total normal cost + Crashing cost + Total indirect cost

$=4000+\underset{}{\underset{}{200\times 2}}+\underset{}{\underset{}{300\times 2}}+\underset{}{\underset{}{100\times 2}}+300\times 1$

'C' by 'A' by 'B' by
2 days 1 day 2 days

= 4000 + 900 + 3000 = 7900/-