Permutation problem

Let x e Za and ye Zb. When a function f:Za Zb is chosen at random, what is Pr[f(x) = y] (ie, the probability that f(x) is y)? Express your answer numerically using plain text without spaces. Use / and ^ and ! to represent division, exponentiation and factorial. Use parenthesis around a term only if it is necessary. Examples: 1/(x-1), (x-3)/10, x!, (x-1)!, x^2, 2^(x-1), etc. Let x e Za and ye Zb. When a function f:Za Zb is chosen at random, what is Pr[f(x) = y] (ie, the probability that f(x) is y)? Express your answer numerically using plain text without spaces. Use / and ^ and ! to represent division, exponentiation and factorial. Use parenthesis around a term only if it is necessary. Examples: 1/(x-1), (x-3)/10, x!, (x-1)!, x^2, 2^(x-1), etc