Consider the Go-Back-N (GBN) protocol with a sender window size of 3 and a sequence number range of 1024. Suppose that at time t, the next in-order packet that the receiver is expecting has a sequence number of k. Assume that the medium does not reorder messages. Answer the following questions:a. (10%) What are the possible sets of sequence numbers inside the sender’s window at time t? Justify your answerb. What are all possible values of the ACK field in all possible messages cur- rently propagating back to the sender at time t? Justify your answer.