Question

A project has four activities P, Q, R and S as shown below.

Activity	Normal duration (days)	Predecessor	Cost slope (Rs./day)
P	3	-	500
Q	7	P	100
R	4	P	400
S	5	R	200

The normal cost of the project is Rs. 10,000/- and the overhead cost is Rs. 200/- per day. If the project duration has to be crashed down to 9 days, the total cost (in Rupees) of the project is

• A. 12500

Answer 1

The correct option is A 12500
Before crashing:

$\text{TC = 10000 + 200 × 12 = Rs. 12400}$


Since cost slope of activity S is minimum.

So, activity S will be crashed by 2 days.

$\text{1st Crashing:}$

$\mathrm{TC}=12400-\underset{\mathrm{overhead}\mathrm{cost}}{\underset{}{200\times 2}}+\underset{\mathrm{crashing}\mathrm{cost}}{200\times 2}$
$=Rs.12400$

$\text{2nd crashing:}$

From various combinations/options, we get, least cost slope in Q + S activity

$\therefore \text{Crashing, Q and S by 1 day each}$

$\text{TC = 12400 - 1 × 200 + 1 × 300}$

$=Rs.12500$