HDU 2289 Cup

The WHU ACM Team has a big cup, with which every member drinks water. Now, we know the volume of the water in the cup, can you tell us it height?

The radius of the cup's top and bottom circle is known, the cup's height is also known.

#include
#include
using namespace std;
const double Pi=acos(-1.);
int main()
{
	int tt;
	cin>>tt;
	while(tt--)
	{
		double r1,r2,h,v;
		cin>>r1>>r2>>h>>v;
		double low,high,mid;
		low=0;
		high=100.;
		for(int i=0;i<100;i++)
		{
			mid=(high+low)/2.;
			double t=r1+(r2-r1)*mid/h;
			double v1=Pi*mid*(t*t+t*r1+r1*r1)/3.;
			if(v1>v)
			high=mid;
			else
			low=mid;
		}
		printf("%.6lfn",mid);
	}

	return 0;
}