Air recycle during drying. The following flowsheet shows the process of drying wood

particles. Wet particles enter the dryer at $25$ weight $\%$ water $($wet basis moisture content$)$

and exit the dryer at $5$ weight percent water $($wet basis moisture content$).$ Ambient air

which is $4\mathrm{.}73$ mole $\%$ water is mixed with recycled air before the mixture enters the dryer.

Part of the moist air from the dryer $(9\mathrm{.}31$ mole $\%$ water$)$ is recycled and the rest is released

to the atmosphere.

Question:

What is the amount of recycle air $($in pound$-$moles$)$ per $100$ pounds of dry particles if the

concentration of water in the air entering the dryer is $5\mathrm{.}20$ mole$\%?$