we know that for pure aloha efficiency = $G \times e^{-2G}$
and in the maximum case we find it to be $0.184$
throughput=efficiency $\times$ Bandwidth
=$.184*19.2=3.5328kbps$
if we find it in packets/sec then,3.5328/packet size=3.5328/100=.035328 kilo packets per second