At timeout time congestion window size is 40KB.
So,New Threshold=40KB/2=20KB.
Now,start from 0 KB exponentially increasing upto Threshold.
0kb-2kb,2kb-4kb,4kb-8kb,8kb-16kb,16kb-20kb(here 16kb-32kb is not possible because it exceed Thrshold),
And now increase only one MSS at a time
20kb-22kb,22kb-24kb,24kb-26kb,26kb-28kb,28kb-30kb,30kb-32kb,32kb-34kb,34kb-36kb,36kb-38kb,38kb-40kb.
Total 15 times.
so total time=RTT*15
RTT=2*PD=2*200msec=400msec.
total time=15*400=6000msec.