Three Critical Path Activities Are Candidates for Crashing on a CPM

Three critical path activities are candidates for crashing on a CPM network. Activity details are in the table below.
$$\begin{array} { | c | c | c | c | c | } \hline \text { Activity } & \text { Normal Time } & \text { Normal Cost } & \begin{array} { c } \text { Crash } \\\text { Duration }\end{array} & \text { Crash Cost } \\\hline \text { A } & 9 \text { days } & \$ 8,000 & 7 \text { days } & \$ 12,000 \\\hline \text { B } & 5 \text { days } & \$ 2,000 & 3 \text { days } & \$ 10,000 \\\hline \text { C } & 12 \text { days } & \$ 9,000 & 11 \text { days } & \$ 12,000 \\\hline\end{array}$$
a. What is the crash cost per unit time for activity A?
b. What is the crash cost per unit time for activity B?
c. Which activity should be crashed first to cut one day from the project's duration; how much is added to project cost?
d. Which activity should be the next activity crashed to cut a second day from the project's duration; how much is added to project cost?
e. Assuming no other paths become critical, how much can this project be shortened at what total added cost?