A fish in an aquarium approaches the left wall at a rate of $2.5 \;m/s$ observes a fly approaching it at $8 m/s$ If the refractive index of water is $(4/3)$ . Then the actual velocity of fly is

Question

$(a)\;2.75\;m/s \\ (b)\;4.75\;m/s \\ (c)\;3.75\;m/s \\ (d)\;1.75\;m/s $