An Electrical Contracting Company Has Been Awarded a Government Contract

An electrical contracting company has been awarded a government contract to install lighting fixtures on a major highway. They want to use a horizontal bar chart to plan the schedule for the contract with work to begin on January 1 and assuming four weeks per month. The company has established the following project activities, their precedence relationships, and their estimated normal times:
$$\begin{array} { l c c } \text { Activity } & \text { Immediate Predecessors } & \underline { \text { Normal Time weeks) } } \\\hline \text { a. order materials } & \text { none } & 4 \\ \text { b. clear job sites } & \text { none } & 6 \\ \text { c. excavate job sites } & \mathrm { b } & 10 \\ \text { d. make trenches for conduit } & \mathrm { b } & 6 \\\text { e. install conduit } & \mathrm { d } & 10 \\ \text { f. form and pour foundations } & c , d & 8 \\ \text { g. install wire } & \mathrm { f } & 6 \\ \mathrm { h } \text {. install lighting standards } & \text { g } & 5 \\ \text { i. install luminaries } & \mathrm { h } & 4 \\\text { j. connect to service } & \mathrm { i } & 3 \\\end{array}$$
a. When does activity d begin?
b. When does activity f end?