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

$[5]$

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$]]],[A,\backslash$table$[[$Closing road$]],5,-],[$B$,$Temporary fencing,$10,A$