#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
template <typename ...T>
void debug_(const char *s, T ...a) {
    cerr << "\e[1;32m(" << s << ") = (";
    int cnt = sizeof...(T);
    (..., (cerr << a << (--cnt ? ", " : ")\e[0m\n")));
}
template <typename I>
void orange_(const char *s, I L, I R) {
    cerr << "\e[1;32m[ " << s << " ] = [ ";
    for (int f = 0; L != R; L++)
        cerr << (f++ ? ", " : "") << *L;
    cerr << " ]\e[0m\n";
}
#else 
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

    using llf = long double;
    int T;
    cin >> T;
    while (T--) {
        int n;
        cin >> n;
        vector<llf> p(n);
        for (int i = 0; i < n; i++) {
            cin >> p[i];
        }

        sort(p.begin(), p.end());
        if (p.back() == 1) {
            cout << 1 << '\n';
            continue;
        }

        llf ans = p.back();

        llf prod = 1, sum = 0;
        for (int i = 0, r = 0; i < n; i++) {
            while (r < n && prod * sum <= (prod * (1 - p[r]) * (sum + p[r] / (1 - p[r])))) {
                prod *= (1 - p[r]);
                sum += p[r] / (1 - p[r]);
                ++r;
                ans = max(ans, prod * sum);
            }
            prod /= 1 - p[i];
            sum -= p[i] / (1 - p[i]);
            ans = max(ans, prod * sum);
        }

        cout << fixed << setprecision(20) << ans << '\n';
    }
    return 0;
}