Mr. Weiland Lava Problem Hart & Grove

After 34 years of being dormant, Mt. St. Helen as erupted over its conical shape at a rate of 8000 ft^2/s. Sadly, a herd of beavers lives nearby. In order to live, these beavers must stay 34 ft away from the lava. How fast must they run if the slope in which they are running down is 698 ft and the height and radius are the same?