#include <iostream>
#include <vector>
#include <string>
#include <iomanip>
#include <queue>
#include <cmath>
#include <algorithm>
#include <tuple>
#include <iomanip>
#include <stdio.h>
#include <numeric>
#include <map>
#include <math.h>

#define int long long
#define ull unsigned long long
#define all(a) a.begin(), a.end()
#define pii pair<int, int>
#define pb push_back

using namespace std;

void solve() {
    int k, n, a, b;
    cin >> k >> n >> a >> b;
    int ans = 0;
    if ((int)k / b <= n) {
        cout << -1 << "\n";
    } else {
//        while ((int)k/a < n) {
//            n--;
//            k-=b;
//        }
//        ans = k/a;
//        if (k % a == 0) {
//            ans--;
//        }
//        cout << min(ans, n) << "\n";
        int r = n, l = 0, mid;
        while (r - l > 1) {
            mid = (l + r) / 2;
//            cout << mid * a + (n - mid) * b << "\n";
//            cout << l << " " << r << "\n";
            if (mid * a + (n - mid) * b >= k) {
                r = mid;
            } else {
                l = mid;
            }
        }
//        cout << l << " " << r << " " << mid << "\n";
        if(r * a + (n - r) * b == k) cout << r - 1;
        else if (r * a + (n - r) * b < k) cout << r;
        else if (mid * a +(n - mid) * b == k) cout << mid - 1;
        else if (mid * a +(n - mid) * b < k) cout << mid;
        else if (l * a + (n - l) * b == k) cout << l - 1;
        else if (l * a + (n - l) * b < k) cout << l;
        cout << "\n";
    }
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
//    cout << fixed << setprecision(3);
    int q;
    cin >> q;
//    vector<int> a(n);
//    for (int i = 0; i < n; i++) cin >> a[i];
    for (int w = 0; w < q; w++) solve();
}