#include<bits/stdc++.h>
using namespace std;
const int N=105;
int n,Case;
long double V,T,s[N];
struct node{long double r,t;}a[N];
bool chk(long double x) {
	long double nv=0,mnt=0,mxt=0;
	for(int i=1;i<=n;i++) {
		long double s=a[i].r*x;
		if(nv+s>V){mnt+=(V-nv)*a[i].t,nv=V;break;}
		else mnt+=s*a[i].t,nv+=s;
	}
	if(nv<V)return 0;
	mnt/=V,nv=0;
	for(int i=n;i;i--) {
		long double s=a[i].r*x;
		if(nv+s>V){mxt+=(V-nv)*a[i].t,nv=V;break;}
		else mxt+=s*a[i].t,nv+=s;
	}mxt/=V;
	return mnt<=T&&mxt>=T;
}
void solve() {
	scanf("%d%Lf%Lf",&n,&V,&T);
	for(int i=1;i<=n;i++)scanf("%Lf%Lf",&a[i].r,&a[i].t);
	long double l=0,r=1e8,mid,ans=-1;sort(a+1,a+n+1,[](const node&x,const node&y){return x.t<y.t;});
	for(int i=1;i<=200;i++)mid=(l+r)/2,chk(mid)?r=mid,ans=mid:l=mid;
	if(ans<0)printf("Case #%d: IMPOSSIBLE\n",++Case);
	else printf("Case #%d : %.8Lf\n",++Case,ans);
}
int main() {
	int tt;scanf("%d",&tt);
	while(tt--)solve();
	return 0;
}