$(3)(4$ nts$)$ Two stations A and B are directly connected and uses a window scheme for error

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y in their data link layer protocol. The protocol uses $4$ bits to represent the packet ID$.$

Assume that $A$ is the sender and $B$ is the receiver and that the sending window and the receiving

window have the size of $5.$ The current sending window is $2,3,4,5,6$ and the receiving window

is $3,4,5,6,7.($a$)$ Assume all three packets arrive at $B$ correctly. What is the new receiver

window of B after this event? $($b$)$ Now A transmits three packets, $2,3,4.$ Assume during the

transmission of the three packets, lighting strikes and packets $2$ and $3$ are destroyed. But packet $4$

arrives at B correctly. What is the new receiver window of B after this event?