$3.$ Suppose an Ethernet packet represents a TCP acknowledgment; that is$,$ the packet contains an IPv$4$ header with no options and a $20-$byte TCP header but nothing else. Is the IPv$4$ packet here smaller than the Ethernet minimum packet size, and, if so$,$ by how much? What if the packet is IPv$6$ with no extension headers?

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$4.$ In newer implementations, repeat ARP queries about a timed out entry are first sent unicast, in order to reduce broadcast traffic. What would have to happen to create a situation where the repeated unicast query for a given IP address fails, but a follow$-$up broadcast query for that same IP address succeeds?