To measure the amount of nickel in some industrial waste fluid, an analytical chemist adds $0\mathrm{.}3400$M sodium hydroxide $($NaOH$)$ solution to a $21\mathrm{.}0$ g sample of the fluid and collects the solid nickel$($II$)$ hydroxide $($Ni$($OH$)2)$ product. When no more Ni$($OH$)2$ is produced, he filters, washes and weighs it$,$ and finds that $0\mathrm{.}261$ g has been produced.The balanced chemical equation for the reaction is: Ni$2+($aq$)+2$NaOH$($aq$)->$ Ni$($OH$)2($s$)+2$ Na$+($aq$)$ What kind of reaction is this? precipitation acid$-$base or redox. If you said this was a precipitation reaction, enter the chemical formula of the precipitate.If you said this was an acid$-$base reaction, enter the chemical formula of the reactant that is acting as the base.If you said this was a redox reaction, enter the chemical symbol of the element that is oxidized.Calculate the mass percent of Ni in the sample. Be sure your answer has $3$ significant digits.