A large open tank has two holes in the wall. One is a square hole of side $'L'$ at a depth $'y'$ from the top and the other is a circular hole of radius R at a depth $'4y'$ from the top. When the tank is completely filled with water, the quantities of water flowing out per second from the two holes are the same. Then value of R is :

Question

$$\begin {array} {1 1} (a)\;\frac{L}{\sqrt {2 \pi}} & \quad (b)\;2 \pi L \\ (c)\;L \sqrt {\frac{2}{\pi}} & \quad (d)\;\frac{L}{2 \pi} \end {array}$$