$1.$ What valid host range is the IP address $172\mathrm{.}21\mathrm{.}149\mathrm{.}224/23$ a part of$?$

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$2.$ What is the first valid host on the subnetwork that the node $192\mathrm{.}168\mathrm{.}247\mathrm{.}251/26$ belongs to$?$