#include<bits/stdc++.h>
using namespace std;
void solve()
{
    int n,h;
    cin>>n>>h;
    pair<int,int>a[n];
    for(int i=0;i<n;i++)
    {
        cin>>a[i].second;
    }
    for(int i=0;i<n;i++)
    {
        cin>>a[i].first;
    }
    sort(a,a+n);
    int ans=0;
    h++;
    for(int i=n-1;i>=0;i--)
    {
        int req=(h+a[i].first-1)/a[i].first;
        int k1=min(req,a[i].second);
        ans+=k1;
        h-=k1*a[i].first;
        if(h<=0)
        {
            break;
        }
    }
    if(h>0)
    {
        cout<<"-1"<<endl;
        return;
    }
    cout<<ans<<endl;
    return;

}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        solve();
    }
}