Let $A = \{1,2,3,4,5,6\}$ and $B = \{a,b,c,d,e\}$. How many functions $f : A \rightarrow B$ are there such that for every $x \in A$, there is one and exactly one $y \in A$ with $y \neq x$ and $f(x) = f(y)$? (A) 450 (B) 540 (C) 900 (D) 5400.
Let $A = \{1,2,3,4,5,6\}$ and $B = \{a,b,c,d,e\}$. How many functions $f : A \rightarrow B$ are there such that for every $x \in A$, there is one and exactly one $y \in A$ with $y \neq x$ and $f(x) = f(y)$?\\
(A) 450\\
(B) 540\\
(C) 900\\
(D) 5400.