a$.$ With the aid of an example, explain the term project crashing with reference to critical path duration of a project.

b$.$ Avenal Construction $\frac{P}{L}$ is awarded a contract to put a medium sized bridge across Save River by Chibi Turn$-$off, and the activities it has to undertake to completion are given with the respective activity precedence as shown in Table Q$5$:

Table Q$5$: Bridge Construction Activity Precedence

$\backslash$table$[[$Activity$,$Activity Description,Duration,$\backslash$table$[[$Immediate$],[$Predecessors$]]],[$Closing road,$5,-],[$B$,$Temporary fencing,$10,$A$],[$C$,$Excavating,$12,$A$],[$D$,$Erection of scaffoldings,$4,$B and C$],[$E$,$Lowering steel work,$8,$C$],[$F$,$Casting of concrete works,$10,$C$],[$G$,$Removing steel works off the site,$10,$E and D$],[$H$,$Remove temporary fence,$4,$B$],[$J$,$Reopening the road,$5,$E and F$],[$K$,$Clearing the site,$1,$H$,$ G$,$ and J$]]$

i$)$ Construct the network diagram for the above activities.

$[5]$

ii$)$ Schedule the earliest start and earliest finish, as well as latest start and latest finish for each activity.

iii$)$ What is the critical duration for this project?

$[6]$

iv$)$ If activity $F$ is extended to duration of $15$ days, what is the effect on the critical path? $[5]$