#include <bits/stdc++.h>
 
using namespace std;
 
const int MaxN = (int)1e5 + 10;
const int MOD = (int)1e9 + 7;
const int INF = 1e9;
 
int n, a, b;
int x[MaxN];
 
void solve() {
	scanf("%d%d%d", &n, &a, &b);
	assert (1 <= n && n <= 1e4);
	int aa = 0, bb = 0;
	for (int i = 1; i <= n; ++i) {
		scanf("%d", &x[i]);
		assert (1 <= x[i] && x[i] <= n);
		if (x[i] == a) {
			aa++;
		}
		if (x[i] == b) {
			bb++;
		}
	}
	long long num = 1LL * aa * bb;
	long long den = 1LL * n * n;
	cout.precision(10);
	cout << fixed << 1.0 * num / den << "\n";
}
 
int main() {
//	freopen("input.txt", "r", stdin);
//	ios::sync_with_stdio(false); cin.tie(NULL);
	int t;
	scanf("%d", &t);
	assert (1 <= t && t <= 70);
	while (t --> 0) {
		solve();
	}
	return 0;
}