$11\mathrm{.}21$ Fresh air containing $0\mathrm{.}01kg$ of water $\frac{?}{kg}$ of dry air is mixed with recycled air containing $0\mathrm{.}15kg$ of water $kg$ of dry air and is blown over a wet solid in a drier. In a certain operation, the wet solid contains $15\%($weight$)$ moisture and it is to be dried to a final moisture content of $5\%$ by evaporating moisture into the air blown over it$.$ The fresh air and recycled air are mixed in such proportions that the air blown over the solid contains $0\mathrm{.}03kg$ of moisture $\frac{?}{kg}$ of dry air. A part of the air leaving the drier which contains $0\mathrm{.}1kg$ of water is recycled. For $100kg$ of wet material charged, determine:

$($a$)$ The ratio of dry air in the recycled air to that in the fresh air AnAnd: $1$:$6$

$($b$)$ The quantity of dry air in the fresh air feed Ans:$75\mathrm{.}79kg$

$($c$)$ The amount of dry air recycled. Ans:$12\mathrm{.}53kg$m