$9.$ Ammonium nitrate $($NH$$NO$)$ is used as a nitrogen source in a fertilizer blend. If the blend needs to contain $80$ kg of nitrogen, and ammonium nitrate contains $35\%$ nitrogen by mass, how much ammonium nitrate is required?

$10.$ A fertilizer mixture is made by blending ammonium sulphate $(($NH$)$SO$)$ and urea $($CO$($NH$))$ to achieve a nitrogen content of $30\%$ by weight. If $200$ kg of the mixture is prepared, and ammonium sulphate contains $21\%$ nitrogen, how much urea is needed if urea is $46\%$ nitrogen by mass?