Im having problems in this question, i have asked my friends and teachers but they dk either, please help!!
Let A = {1,2,3,4}. The number of functions f: S ---> S. Such that f(f(i) = i for all 1<= i <= 4 is?
Im getting the answer 24 (4!) by applying the condition that the function must be bijective as its inverse exists. But the answer is 10