Networking course

A sender having window size=2 transmits at 1 million bits per second. The packet size is 1000 bits and the round trip RTT= 4 ms between the sender and receiver. The sender starts a timer for a packet when it finishes transmitting it, and uses a timeout of 4 ms. The receiver sends an acknowledgement after it receives the last bits of the packet. The sender needs to send 6000 bits. The first bits is transmitted at t=0. At what time the last bits arrive to the sender