Ali Sdn$.$ Bhd$.$ is a construction company. The company recently received a contract to build a mini garden in a shopping mall. The activities involved in constructing the mini garden are shown in Table $1.$

Table $1$: Activities and all data for each activity

a$)$ Calculate expected time and variance for each activity.

b$)$ Construct a network diagram based on Activity$-$on$-$Node $($AON$)$ for the mini garden project and determine the minimum time to complete the whole project. Highlight critical path$($s$)$ in the drawn network diagram.

c$)$ If the project should be shortened for two $(2)$ months, determine which activities should be crashed. Determine the new completion time, critical activities and the minimum crashing cost incurred.