/** gnu specific **/
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
/** contains everything I need in std **/
#include <bits/stdc++.h>

#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(S) ((int)S.size())
#define FOR(i, st_, n) for(int i = st_; i < n; ++i)
#define RFOR(i, n, end_) for(int i = (n)-1; i >= end_; --i)
#define x first
#define y second
#define pb push_back
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef pair<double, double> pdd;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ull, ull> pull;
using namespace __gnu_pbds;
typedef tree<ll, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
using namespace std;
typedef ll int_128;
#ifdef ONPC
mt19937 rnd(228);
#else
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    ll t;
    cin >> t;
    ll c = 100000;
    FOR(_,0,t)
    {
        ll n,k,a,b;
        cin >> k >> n >> a >> b;
        ll res = 0;
        ll cur;
        if(k*(b-a) < a)
        {
            res = -1;
        }
        else {
        while(n > 0)
        {
            cur = (k*(b-a))/a;
            if(((k+cur*c)*(b-a))/a == cur)
            {
                if(n < cur * c)
                {
                    c = n/cur;
                }
                k+= cur*c;
                res+= c;
                n-= cur*c;
            }
            if(n <= 0)
                break;
            //cout << k << ' ';
            n -= (k*(b-a))/a;
            k += (k*(b-a))/a;
            res++;
        }
        }
        cout << res << endl;
    }
}