Let f(x,y) be defined as the remainder when (x–y)! is divided by x. If x=50, what is the maximum value of y for which f(x,y)=0?  Choose the correct choice from the following.
A) 35
B) 36
C) 40
D) 42
E) 45
The question is finding y such that (50-y)! is a multiple of 50. That means we need to have 2*5^2 in (50-y)!   10! is the smallest factorial number with 2*5^2 as a factor.   50-y = 10   y = 40   The answer is 40.
<result>C</result>
Let f(x,y) be defined as the remainder when (x–y)! is divided by x. If x=50, what is the maximum value of y for which f(x,y)=0?