#pragma GCC optimize("O3")
#include <iostream>
#include <cmath>
using namespace std;
const int mx=100000;
typedef long long ll; const ll inf=9e18;
ll x[mx+1], y[mx+1];
void eq(ll u, ll v, ll& a0, ll& a1)
{
    //ux+v >= 0
    if(!u&&v<0) a1=-1;
    if(u>0) a0 = max(a0,ll(ceil((-1.0*v)/u)));
    if(u<0) a1 = min(a1,ll(floor((-1.0*v)/u)));
}
ll solve()
{
    int n; ll k, X,Y, ans=inf; cin>>n>>k>>X>>Y;
    for(int i=1; i<=n; i++) cin>>x[i]>>y[i], x[i]+=x[i-1], y[i]+=y[i-1];
    for(int i=0; i<n; i++)
    {
        ll u=x[n], v=y[n], U=X-x[i], V=Y-y[i], a0=0, a1=inf;
        //dist (ua,va) (U,V) <= nka + ki
        eq(n*k-u-v,k*i+U+V,a0,a1);
        eq(n*k-u+v,k*i+U-V,a0,a1);
        eq(n*k+u-v,k*i-U+V,a0,a1);
        eq(n*k+u+v,k*i-U-V,a0,a1);
        if(a1>=a0) ans=min(ans,a0*n+i);
    }
    return (ans==inf)?-1:ans;
}
int main()
{
    cin.sync_with_stdio(0), cin.tie(0), cout.sync_with_stdio(0), cout.tie(0);
    int T; cin>>T; while(T--) cout<<solve()<<'\n';
}