Question 126
What is the minimum number of successive swaps of adjacent letters in the string $ABCDEF$ that are needed to change the string to $FEDCBA$? (For example, 3 swaps are required to change $ABC$ to $CBA$; one such sequence of swaps is $ABC \to BAC \to BCA \to CBA$.)
(A) 6 (B) 10 (C) 12 (D) 15 (E) 24
(A) 6 (B) 10 (C) 12 (D) 15 (E) 24