$2.[10$ points$]$ You are assembling your new scanning mobility particle sizer $($SMPS$),$ which consists of an impactor to limit the entry of large particles into your system, a differential mobility analyzer $($DMA$)$ to characterize the size of incoming particles, and a condensation particle counter $($CPC$)$ to count incoming particles.

a$.[8$ points$]$ You install a conventional impactor on your SMPS inlet. You are interested in studying particles from $5$ nm up to $\backslash (0\mathrm{.}5\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash )$ in diameter. The flow rate into your impactor is $\backslash (1\backslash$mathrm$\{$~L$\}/\backslash$mathrm$\{$min$\}\backslash )($this is your "aerosol flow rate"$).$ You have any round nozzle diameter available to you to pull from the shelf and install. Which nozzle diameter would you choose? Assume laminar flow. Note: you can also choose your desired collection efficiency. Clearly state your collection efficiency choice and your nozzle diameter choice.

b$.[2$ points$]$ From the data we collected during the SMPS demo, which flow rate settings would be most compatible with this scenario? Why?