In: Operations Management
Consider the following precedence chart:
| ACTIVITY | PRECEDING ACTIVITIES | OPTIMISTIC TIME (days) | MOST LIKELY TIME (days) | PESSIMISTIC TIME (days) | 
| A | - | 5 | 10 | 15 | 
| B | - | 10 | 12 | 14 | 
| C | - | 10 | 10 | 10 | 
| D | B,C | 2 | 4 | 6 | 
| E | A | 4 | 8 | 12 | 
| F | A | 4 | 8 | 12 | 
| G | D,E | 10 | 12 | 14 | 
| I | F | 4 | 8 | 12 | 
| J | G | 2 | 4 | 6 | 
The total slack for activity C is __________
| a. | 
 0  | 
|
| b. | 
 2  | 
|
| c. | 
 8  | 
|
| d. | 
 4  | 
The expected durations of each activity are presented below :
| 
 Task  | 
 Optimistic (O)  | 
 Most likely ( m)  | 
 Pessimistic(P)  | 
 Expected duration  | 
| 
 A  | 
 5  | 
 10  | 
 15  | 
 10.00  | 
| 
 B  | 
 10  | 
 12  | 
 14  | 
 12.00  | 
| 
 C  | 
 10  | 
 10  | 
 10  | 
 10.00  | 
| 
 D  | 
 2  | 
 4  | 
 6  | 
 4.00  | 
| 
 E  | 
 4  | 
 8  | 
 12  | 
 8.00  | 
| 
 F  | 
 4  | 
 8  | 
 12  | 
 8.00  | 
| 
 G  | 
 10  | 
 12  | 
 14  | 
 12.00  | 
| 
 I  | 
 4  | 
 8  | 
 12  | 
 8.00  | 
| 
 J  | 
 2  | 
 4  | 
 6  | 
 4.00  | 
Expected duration = ( Optimistic duration + 4 x Most likely duration + Pessimistic duration) / 6
The precedence diagram of activities as follows :
| 
 A  | 
 B  | 
 C  | 
|
| 
 F  | 
 E  | 
 D  | 
|
| 
 I  | 
 G  | 
||
| 
 J  | 
|||
The possible parallel paths and their expected durations as follows :
A-F-I = 10 + 8 + 8 = 26
A-E-G-J = 10 + 8 + 12 + 4 = 34
B-D-G-J = 12 + 4 + 12 + 4 = 32
C-D-G-J = 10 + 4 + 12 + 4 = 30
Since A-E-G-J has the longest Expected duration, it forms the critical path.
Slack for activities C, D
= Duration A-E-G-J – Duration C-D-G-J
= 34 – 30 DAYS
= 4 days
| 
 TOTAL SLACK FOR ACTIVITY C = 4 DAYS  |