Two identical balls having like charges and placed at a certain distance apart repel each
other with a certain force. They are brought in contact and then moved apart to a distance
equal to half their initial separation. The force of repulsion between them increases 4.5
times in comparison with the initial value. The ratio of the initial charges of the balls is
........
Options:
(a) 4 : 1
(b) 6 : 1
(c) 3 : 1
(d) 2 : 1