#include <bits/stdc++.h>
using namespace std;
#define int long long 
const int oo = 1'000'000'000'000'000'000ll;
int n,k,X,Y;
vector<int>xs,ys;
int sumx,sumy;
unordered_map<int,int>memo;
int getmin(int rounds){
	if(memo.find(rounds) != memo.end())return memo[rounds];
	int hx=sumx*rounds,hy=sumy*rounds;
	int curdiff=abs(hx-X)+abs(hy-Y);
	int idx=rounds*n;

	if(curdiff<=k*idx)return idx;
	for(int i=0;i<n;i++){
		hx+=xs[i];
		hy+=ys[i];
		int curdiff=abs(hx-X)+abs(hy-Y);
		int idx=rounds*n+i+1;
		
		if(curdiff<=k*idx)return idx;
	}
	return oo;
}
void solve(){
	cin>>n>>k>>X>>Y;
	xs.clear();ys.clear();
	memo.clear();
	sumx=0;sumy=0;
	for(int i=0;i<n;i++){
		int v1,v2;cin>>v1>>v2;
		sumx+=v1;sumy+=v2;
		xs.push_back(v1);
		ys.push_back(v2);
	}

	int ans=oo;
	set<int>impt;
	impt.insert(0);
	if(sumx){
		int rf=X/sumx;
		rf=max(0ll, rf);
		impt.insert(rf);
		impt.insert(rf+1);
	}
	if(sumy){
		int rf=Y/sumy;
		rf=max(0ll,rf);
		impt.insert(rf);
		impt.insert(rf+1);
	}
	impt.insert(1'000'000'000);
	for(auto x:impt){
		ans=min(ans,getmin(x));
	}
	
	vector<int>vs;
	for(auto x:impt)vs.push_back(x);
	for(int i=0;i<(int)vs.size()-1;i++){
		if(true){
			int lo=vs[i],hi=vs[i+1];
			while(lo<hi-1){
				int mi=(lo+hi)/2;
				int res=getmin(mi);
				ans=min(ans,res);
				if(res!=oo)hi=mi;
				else lo=mi;
			}
		}
	}
	
	if(ans==oo)cout<<-1<<"\n";
	else cout<<ans<<"\n";
}
int32_t main(){
	ios_base::sync_with_stdio(0);cin.tie(0);
	int T; cin>>T;
	while(T--)solve();
}