#include <fstream.h>
#include <search.h>
#include <iomanip.h>
#define in cin
struct BP{
int b;
int p;
};
BP my[100][100];
int n,m;
int len[100];
int blen;
int bs[10001];
int compare(const void* a,const void *b){
return (*(BP*)a).b-(*(BP*)b).b;
}
int comp(const void* a,const void *b){
return (*(int*)a)-(*(int*)b);
}
void getData(){
int i,j,k;
in>>m;
for(i=0;i<m;i++){
in>>len[i];
for(j=0;j<len[i];j++)
in>>my[i][j].b>>my[i][j].p;
qsort(my[i],len[i],sizeof(BP),compare);
}
bs[0]=0;k=0;blen=1;
for(i=0;i<m;i++)
for(j=0;j<len[i];j++)
bs[blen++]=my[i][j].b;
qsort(bs,blen,sizeof(int),comp);
}
int getIndex(int row,int t){
int back=25535;
for(int i=0;i<len[row];i++)
if(my[row][i].b>=t&&my[row][i].p<back)
back=my[row][i].p;
return back;
}
void solve(){
int i,j;
double total;
double max=-1;
for(i=1;i<blen;i++){
if(bs[i]==bs[i-1])continue;
total=0;
for(j=0;j<m;j++){
int s=getIndex(j,bs[i]);
if(s<0)
break;
total+=s;
}
if(j<m)continue;
if(max<bs[i]/total)
max=bs[i]/total;
}
cout<<setiosflags(ios::fixed)<<setprecision(3)<<max<<endl;
}
void main()
{
in>>n;
for(int i=0;i<n;i++){
getData();
solve();
}
}