When an air bubble of radius $r$ rises from the bottom to the surface of a lake, its radius becomes $\frac { 5r } { 4 }$. Taking the atmospheric pressure to be equal to 10 m height of water column, the depth of the lake would approximately be (ignore the surface tension and the effect of temperature):\\
(1) 10.5 m\\
(2) 8.7 m\\
(3) 11.2 m\\
(4) 9.5 m