A TCP connection is transferring $6000B$.
- First Byte is numbered as $10010$ as sequence number and carries $1000B$.
- Second byte starts from $10010 + 1000 - 1= 11010$ as sequence number
- Similarly, third byte from $12010$.
- Third byte from $13010$.
- Last byte has sequence number = $14010$ which carries $2000B$
This procedure is done for "If each segment is encapsulated with sequence number", but question asks for each byte,so.
Now, each byte gets a sequence number and sequence number of last segment => $10010 + 6000 - 1$ => 16009$ is the last byte sent .