What is the first valid host on the subnetwork that the node $172\mathrm{.}17\mathrm{.}60\mathrm{.}163/20$ belongs to$?$

Which subnet does host $10\mathrm{.}63\mathrm{.}76\mathrm{.}94255\mathrm{.}255\mathrm{.}240\mathrm{.}0$ belong to$?$

What is the first valid host on the subnetwork that the node $172\mathrm{.}25\mathrm{.}232\mathrm{.}244/21$ belongs to$?$

Which subnet does host $172\mathrm{.}16\mathrm{.}238\mathrm{.}90/23$ belong to$?$

What is the last valid host on the subnetwork $172\mathrm{.}31\mathrm{.}134\mathrm{.}0255\mathrm{.}255\mathrm{.}254\mathrm{.}0?$