A thin lens made of glass (refractive index $= 1.5$) of focal length $f = 16 \mathrm {~cm}$ is immersed in a liquid of refractive index 1.42. If its focal length in liquid is $f _ { l }$, then the ratio $f _ { l } / f$ is closest to the integer:\\
(1) 1\\
(2) 9\\
(3) 5\\
(4) 17