#include? < iostream >
#include? < set >
#include? < limits >

using ? namespace ?std;

struct ?Node
{
???? int ?broad,?price;
????Node() {}
????Node( int ? & a, int & b)
????????:broad(a),price(b)
???? {}
} ;

Node?data[ 100 ][ 100 ];
int ??length[ 100 ];


int ?main()
{
???? int ?test;
????scanf( " %d " , & test);

???? while (?test -- ?)
???? {
???????? int ?n;
???????? set < int > ?br;

????????scanf( " %d " , & n);

???????? for ?(? int ?i = ? 0 ;?i < ?n;? ++ i?)
???????? {
???????????? int ?d,x,y;
????????????scanf( " %d " , & d);

????????????length[i] = ?d;
???????????? for ?(? int ?j = ? 0 ;?j < ?d;? ++ j?)
???????????? {
????????????????scanf( " %d%d " , & x, & y);
????????????????data[i][j] = ?Node(x,y);

????????????????br.insert(x);???? // ???Save?all?broad?,?use?set?to?avoid?repeating
????????????}
????????}

???????? set < int > ::iterator?pos;
???????? double ?max = ?numeric_limits < double > ::min();
???????? for ?(?pos = ?br.begin?();?pos != ?br.end?();? ++ pos?)??? // ???for?every?broad
???????? {
???????????? int ???t = ? * pos;
???????????? int ???total = ? 0 ;
???????????? bool ??isok = ? false ;

???????????? for ?(? int ?i = ? 0 ;?i < ?n;? ++ i?)??? // ??n?devices
???????????? {
???????????????? int ?M = ?INT_MAX;

???????????????? for ?(? int ?j = ? 0 ;?j < ?length[i];? ++ j?)
???????????????????? if ?(?data[i][j].broad >= ?t? && ?data[i][j].price < ?M?)
????????????????????????M = ?data[i][j].price;?????? // ???find??the?min?price

???????????????? if ?(?M == ?INT_MAX?)
???????????????? {
????????????????????isok = ? true ;
???????????????????? break ;
????????????????}
????????????????total += ?M;?????
????????????}

???????????? if ?(?isok?)? continue ;

???????????? if ?(?( double )t / ?( double )total > ?max?)?max = ?( double )t / ?( double )total;??? // ??update
????????}

????????printf( " %.3lf\n " ,?max?);
????}

???? return ? 0 ;
}