#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
long long n,k,x,y,lo,hi,mid1,mid2,j;
__int128 a1,a2,v1,v2;
pair<long long,long long> arr[100005];
pair<long long,long long> net;
int32_t main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int t;
	cin >> t;
	while(t--){
		long long in;
		long long ik,ix,iy;
		cin >> in >> ik >> ix >> iy;
		n=in,k=ik,x=ix,y=iy;
		net={0,0};
		for(int i=0; i<n; i++){
			long long a,b;
			cin >> a >> b;
			arr[i].first=a; arr[i].second=b;
			net.first+=arr[i].first;
			net.second+=arr[i].second;
			if(i) arr[i].first+=arr[i-1].first,arr[i].second+=arr[i-1].second;
		}
		if(x==0&&y==0){
			cout << 0 << '\n';
			continue;
		}
		long long iters[n];
		memset(iters,-1,sizeof(iters));
		for(int i=0; i<n; i++){
			lo=0,hi=1e13;
			while(hi-lo>2){
				mid1=(lo*2ll+hi)/3ll;
				mid2=(lo+hi*2ll)/3ll;
				//cout << lo << ' ' << mid1 << ' ' << mid2 << ' ' << hi << '\n';
				a1=x-(arr[i].first+(__int128)mid1*net.first),a2=y-(arr[i].second+(__int128)mid1*net.second);
				if(a1<0) a1=-a1;
				if(a2<0) a2=-a2;
				v1=a1+a2-(i+1+(__int128)mid1*n)*k;
				if(v1<=0){
					hi=mid2;
					continue;
				}
				a1=x-(arr[i].first+(__int128)mid2*net.first),a2=y-(arr[i].second+(__int128)mid2*net.second);
				if(a1<0) a1=-a1;
				if(a2<0) a2=-a2;
				v2=a1+a2-(i+1+(__int128)mid2*n)*k;
				if(v1<=0&&v2<=0) hi=mid2;
				else if(v2>v1) hi=mid2;
				else lo=mid1;
			}
			for(j=lo; j<=hi; j++){
				a1=x-(arr[i].first+(__int128)j*net.first),a2=y-(arr[i].second+(__int128)j*net.second);
				if(a1<0) a1=-a1;
				if(a2<0) a2=-a2;
				v1=a1+a2-(i+1+(__int128)j*n)*k;
				if(v1<=0){
					iters[i]=j;
					break;
				}
			}
		}
		long long ans=1e18+5;
		for(int i=0; i<n; i++){
			//cout << iters[i] << ' ';
			if(iters[i]!=-1) if(ans>iters[i]*n+i+1) ans=iters[i]*n+i+1;
		}
		if(ans>=(long long)1e18) cout << -1 << '\n';
		else cout << ans << '\n';
	}
}