A large number of water drops, each of radius r, combine to form a drop of radius R. If the surface tension is T and the mechanical equivalent of heat is J, the rise in heat energy per unit volume will be :
A. 2T/rJ
B. 4T/rJ
C. 2T/J(1/r−1/R)
D. 3T/J(1/r−1/R)