Answer should be 2600
RTT will be 2*T(p) =200 ns
timeout is at 38 means new thresh hold will be floor(CWND/2)=19 KB
now till `19 kb we will have slow start algo so
we will have 2-4-8-16-19 .
form 19 we will have additive increase
so 19-21-23-25-27-29-31-33-35-37(roughly 36) here we will get congestion window of 36 which is asked in question
total 13 RTT'S
So 13*200=2600ms