$17.$ In an extraction process, the feed contains $10\%$ by weight of the target solute. If $1000$ grams of feed are processed, how much solute is present?

$18.$ If the distribution coefficient for a solute between two phases is $0\mathrm{.}5,$ and the concentration of the solute in the initial phase is $200$ mg$/$L$,$ what is the concentration of the solute in the second phase after equilibrium?

$19.$ During solvent recovery, $85\%$ of the solvent is recaptured from the extraction process. If the initial use was $200$ liters, how many liters of solvent are recovered?

$20.$ A multistage extraction process with $5$ stages achieves a solute recovery of $95\%,90\%,85\%,80\%,$ and $75\%$ in each stage respectively. If the initial solute amount is $100$ grams, how much solute is recovered after all stages?