A countercurrent tunnel dryer is used to dehydrate an aspirin solution.The moisture content is reduced from $83$ w$/$w$\%$ to $7$ w$/$w$\%(=$water$/$air $=$water$/($water$+$dry air$).$ The warm air enters the dryer with an absolute humidity$(=$water$/$dry air$)$ of $10\mathrm{.}5\%$ and leaves the dryer at $13\%.$

Calculate the amount of hot air $($kg$/$h$)$ needed to dry $800$ kg of aspirin solution