Problem #$2$:

$10\mathrm{.}5.$ The flow rate of liquid metal into the downsprue of

a mold $=1\frac{L}{s}.$ The cross$-$sectional area at the top

of the sprue $=800m{m}^2,$ and its length $=175mm.$

What area should be used at the base of the sprue

to avoid aspiration of the molten metal?