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

double pre[10005],suf[10005];
double a[10005];int n;

int main(){
    int T;scanf("%d",&T);
    while(T--){
        int n;scanf("%d",&n);
        for(int i=1;i<=n;i++){
            scanf("%lf",&a[i]);
        }
        sort(a+1,a+n+1);
        // reverse(a+1,a+n+1);
        if(a[n]>=0.5000)
            printf("%.10f\n",a[n]);
        else{
            double ans=a[n],cur=1-a[n];
            for(int i=n-1;i>=1;i--){
                double newans=ans*(1-a[i])+a[i]*cur;
                if(newans>ans)ans=newans;
                else break;
                cur*=1-a[i];
            }
            printf("%.10f\n",ans);
        }
    }
}