A large number of liquid drops each of radius r coalesce to from a single drop radius R.The energy released in the process is converted into kinetic energy of the big drop so formed . The speed of the big drop is (given surface tension of liquid T , density $\;\rho\;$)

Question

$(a)\;\sqrt{\large\frac{T}{\rho}(\large\frac{1}{r}-\large\frac{1}{R})}\qquad(b)\;\sqrt{\large\frac{2T}{\rho}(\large\frac{1}{r}-\large\frac{1}{R})}\qquad(c)\;\sqrt{\large\frac{4T}{\rho}(\large\frac{1}{r}-\large\frac{1}{R})}\qquad(d)\;\sqrt{\large\frac{6T}{\rho}(\large\frac{1}{r}-\large\frac{1}{R})}$