(1)
(2) After RTT = 16, since after setting new threshold congestion avoidance phase is started from threshold therefore message is lost by receiving three repeated ACK.
After RTT = 22, after setting new threshold slow start phase is started therefore message segment is lost by timeout.
(3) At RTT = 1, threshold = 32
At RTT = 18, threshold = 21
At RTT = 24, threshold = 13
(4) After receiving 3 duplicate ACK at RTT =26, Threshold = 4 and since congestion avoidance phase is started from threshold therefore cwnd = 4