$1.$ Suppose the daytime processing load consists of $\backslash (60\backslash \%\backslash )$ CPU activity and $\backslash (40\backslash \%\backslash )$ disk activity. Your customers are complaining that the system is slow. After doing some research, you have learned that you can upgrade your disks for $\backslash (\backslash$$ $8,000\backslash )$ to make them $2\mathrm{.}5$ times as fast as they are currently. You have also learned that you can upgrade your CPU to make it $1\mathrm{.}5$ times as fast as the current CPU for $\backslash (\backslash$$ $5,000\backslash ).$

a$.$ Which upgrade option would give a faster system?

b$.$ Which upgrade option would give the best return of investment for each percent of speed improvement?

Show your calculation to support your conclusion.