$4)$ SunTech Solar is planning to develop a new solar panel prototype. The project consists of several activities with the following data: $\backslash$begin$\{$tabular$\}\{|$l$|$l$|$l$|$l$|$l$|$l$|\}\backslash$hline Activity & Normal Time $($weeks$)$ & Crash Time $($weeks$)$ & Normal Cost $(\backslash$$$)$ & Crash Cost $(\backslash$$$)$ & Immediate Predecessor$($s$)\backslash \backslash \backslash$hline A & $5$ & $3$ & $2000$ & $3500$ & $-\backslash \backslash \backslash$hline B & $4$ & $2$ & $1500$ & $3000$ & $-\backslash \backslash \backslash$hline C & $10$ & $5$ & $1000$ & $2000$ & $-\backslash \backslash \backslash$hline D & $6$ & $4$ & $1200$ & $2200$ & A $\backslash \backslash \backslash$hline E & $5$ & $3$ & $900$ & $1300$ & B $\backslash \backslash \backslash$hline F & $3$ & $1$ & $2500$ & $4000$ & C $\backslash \backslash \backslash$hline G & $7$ & $4$ & $1800$ & $3000$ & D$,$ E $\backslash \backslash \backslash$hline $\backslash$end$\{$tabular$\}$ a$)$ What is the normal project completion time $($in weeks$)?$ b$)$ Crash the project by $6$ weeks. Which activities should be crashed? What is the cost of crashing the project by $6$ weeks $($in addition to the normal cost of project$)?$