$59$ A device has been assigned the IPv$6$ address of $2001$:$0$db$8$:cafe:$4500$:$1000$:$00$d$8$:$0058$:$00$ab$/64.$ Which is the network identifier of the device?

$2001$

$2001$:$0$db$8$:cafe:$4500$:$1000$:$00$d$8$:$0058$:$00$ab

$2001$:$0$db$8$:cafe: $4500$

$2001$:$0$db$8$:cafe:$4500$:$1000$

$1000$:$00$d$8$:$0058$:$00$ab