HarmoniikaaHarmoniikaa HDU 1724

using namespace std;
int T;
double a,b;
double (double x){
  return sqrt((1-(x*x)/(a*a))*(b*b));
}
double simpson(double a,double b){
  double c=(a+b)/2.0;
  return (f(a)+4*f(c)+f(b))*(b-a)/6.0;
}
double asr(double l,double r,double eps,double A){
  double c=(l+r)/2.0;
  double L=simpson(l,c),R=simpson(c,r);
  if(fabs(L+R-A)<=15.0*eps) return L+R+(L+R-A)/15.0;
  return asr(l,c,eps/2,L)+asr(c,r,eps/2,R);
}
int main(){
  scanf("%d",&T);
  while(T--){
    int l,r;
    scanf("%lf%lf%d%d",&a,&b,&l,&r);
    printf("%.3fn",asr(l,r,1e-6,simpson(l,r))*2);
  }
  return 0;
}