HostA has established a TCP connection with HostB in a remote network. HostA is sending packets to HostB. Assume we have configured TCP$,$ somehow, to ACK every segment $($no ACKing every other segment$).$ Assume that the timeout is the same for all packets. HostB$$s $$window size$$ is $20000$ bytes. HostB has already received and acknowledged everything sent by HostA$$s application up to and including byte #$4,978.$ HostA now sends segments of the same application data stream in order:

P: $168$ bytes

Q: $235$ bytes

R: $437$ bytes

Suppose that packet P is lost, but packets Q and R are received. What is the acknowledgement number in the ACK for packet R$.$