host a and b are communicating over a tcp connection, and host b has already received from a all bytes up through byte 126. suppose host a then sends two segments to host b back-to-back. the first and second segments contain 80 and 40 bytes of data, respectively. in the first segment, the sequence number is 127. host b sends an acknowledgment whenever it receives a segment from host a. in the second segment sent from host a to b, what is the sequence number?