From the meaning of the question, it can be concluded that the black ball in A was given to B, and the white ball in B was given to A. In this way, it can be concluded that A is all white balls and B is all black balls, and the number of the two balls is equal. The white balls in C are two-fifths of all balls, and the white balls in C are two. The number of balls in A is three white balls, B is three black balls, and C is 1 black ball, so