What is max time taken by Xbee S2 to send a packet of 24bytes with 115200 baud rate?

[Nini]

I want to send 24bytes of data within a millin seconds( 4 pkts/ms) for my project.But it takes 4 ms/per packet for my project.How to optmize it.Am

Model: Xbee S2C
Protocol: Xbee
No of Xbees - 2
End point - 1
Co - Ordinator - 1
Both are in API mode
Baud rate - 115200
Controller in end Point - arduino nano
Controller in Co-Ordinator - Raspberry Pi