$3.$ A pattern of trenches has to be planned, marked out, dig and filled with concrete made

from dry ingredients which are to be collected in the correct quantities from another

location. The activities involved together with their duration and manpower are as

follows:

Reference Activity Duration $($hours$)$ Men

A Plan layout $21$

B Mark out site $12$

C Dig trenches $33$

D Obtain concrete material $41$

E Mix concrete $12$

F Fill trenches $13$

a$.$ Draw an $$activity on arrow$$ and an $$activity on node$$ network of the project and

determine the critical path and minimum time it will take to complete the project.

b$.$ Construct a bar chart and determine the manpower requirements throughout the

project.

c$.$ Assuming that the digging equipment was taken in error by the vehicle collecting

the concrete material. Draw another $$activity on arrow$$ diagram to show the

affect this would have on the completion of the project.