#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 z; cin >> z;
		sumx+=z;
		xs.push_back(z);
	}
	for(int i=0;i<n;i++){
		int z; cin >> z;
		sumy+=z;
		ys.push_back(z);
	}

	int ans=getmin(0);
	int lo=0,hi=1'000'000'000;
	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();
}