Suppose a stop-and-wait receiver has an implementation flaw. When Data[1] arrives, ACK[1] and ACK[2] are sent, separated by a brief interval; after that, the receiver transmits ACK[N+1] when Data[N] arrives, rather than the correct ACK[N].

(a). Assume the sender responds to each ACK as soon as it arrives. Explain why the sender will not be able to detect this receiver problem until after it has sent its final packet, Data[M], and receives an unexpected ACK[M+1]. Hint: draw a diagram.

(b). Is there anything the transmitter can do to detect this receiver problem earlier?