Vacas a diesel

/*
 * sin título.cxx
 *
 * Copyright 2018  <oia@oia-vb>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 *
 *
 */


#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int DP[10001], N , L,P;
pair<int,int> in[10001];
int Caso()
{
    cin>>N;
    for(int i = 0;i<N;i++)
        scanf("%d %d",&in[i].first,&in[i].second),DP[i] = 0;
    cin>>L>>P;
    DP[N] = 0;
    DP[0] = P;
    for(int i = 0;i<N;i++)
        in[i].first = L - in[i].first;
    sort(in,&in[N]);
    for(int i = 0;i<N;i++)
    {
        for(int j = N-1;j>=0;j--)
        {
            if(DP[j] >= in[i].first && DP[j] + in[i].second > DP[j+1])
                DP[j+1] = DP[j] + in[i].second;
        }
    }
    /*for(int i = 0;i<=N;i++)
        cout<<DP[i]<<" ";
    cout<<endl;*/
    for(int i = 0;i<=N;i++)
        if(DP[i] >= L)
            return i;
    return -1;
}

int main()
{
    #ifdef YO
        freopen("vacas.in","r",stdin);
    #endif
    int T;
    cin>>T;
    while(T--)
        cout<<Caso()<<endl;
}