First transmission: 2KB
Second transmission: 4KB
Third transmission: 8 KB
Fourth transmission: 16 KB
Fifth transmission: 20 KB [ Threshold reached]
Sixth transmission: 22 KB [ Congestion avoidance phase starts]
Seventh transmission: 24 KB
It takes 7 round trip time.
RTT = 2 *Tp = 10 ms = 20 ms
So 7 RTT = 20 x 7 = 140 ms