#include <algorithm>
#include <iomanip>
#include <iostream>
#include <queue>
template<typename T>
void upd_max(T &a, T b) { if (a < b) a = b; }
constexpr int N = 10000;
double P[N];
void solve()
{
    int n; std::cin >> n;
    for (int i = 0; i < n; ++i)
        std::cin >> P[i];
    std::sort(P, P + n, std::greater<>());
    if (P[0] == 1)
    {
        std::cout << "1\n";
        return;
    }
    double ans = 0;
    double s = 0, p = 1;
    for (int i = 0; i < n; ++i)
    {
        s += P[i] / (1 - P[i]), p *= 1 - P[i];
        upd_max(ans, s * p);
    }
    std::cout << ans << "\n";
}
int main()
{
    std::ios::sync_with_stdio(false), std::cin.tie(nullptr);
    int T; std::cin >> T;
    std::cout << std::fixed << std::setprecision(6);
    while (T--) solve();
}