We want to transfer a file of size d bytes. Each link has bandwidth b bits$/$sec and fixed propagation delay f sec$.$ All routers on the path are store$-$and$-$forward. We use packets of total size P bytes, of which h bytes are occupied by headers. We always pad the last packet so that it is full. There is no set$-$up time for the transfer. Packets are sent continuously and are not lost. There is no queuing delay or processing overhead, and we ignore acknowledgments sent back by the receiver.