A TCP segment from Host A to Host B contains bytes $15-29.$ Acknowledgment number for this segment from Host B is $30.$ If Window Size field in this acknowledgment has a value of $40,$ then Host A may send through byte $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.$

$45$

$30($ACK #$,$ which is the next sequence number$)+40($window size$)=70$

$40$

$30($ACK #$,$ which is the next sequence number$)+40($window size$)=70$

$70$