sir round trip time is time of data from sender to receiver+ and time of ack from sender to receiver, since nothing is said about propagation time, u took transfer time only while counting turn around time but sir why have u not multiply it by 2. and for the second part the window size if generally 16 bits but it can be increased by 14 bits making it 30 bits. So sir answer should be 2^30 which is 65536*2^14, why 65536 *2^14