A pulse of tracer was injected into a tubular reactor to determine if the flow was laminar or plug flow. Effluent tracer concentrations were measured over time, and RTD profiles were developed.

$($a$)$ What features of the $F()$ profile distinguish laminar flow from plug flow?

$($b$)$ Assuming laminar flow and a mean residence time of $16$min, how long does it take for half of the injected tracer to pass through the reactor?