A large tank, open at the top, has two small holes in the vertical wall. One is a square hole of side $$s$$ at a depth $$h$$ below the top and the other is a circular hole of radius $$r$$ at a depth $$4h$$ below the top, given that $$s \ll h$$ and $$r \ll h$$. When the tank is completely filled up to the brim with water, the quantity of water flowing out per second from each hole is the same, then $$r$$ is equal to