/*  Erica N  */
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define int long long
#define ull unsigned long long
#define pii pair<int, int>
#define ps second
#define pf first
#define itn int
#define rd read()
int read(){
    int xx = 0, ff = 1;char ch = getchar();
    while (ch < '0' || ch > '9') {if (ch == '-')ff = -1; ch = getchar();}
    while (ch >= '0' && ch <= '9')xx = xx * 10 + (ch - '0'), ch = getchar();
    return xx * ff;
}
// void write(int out) {
// 	if (out < 0)
// 		putchar('-'), out = -out;
// 	if (out > 9)
// 		write(out / 10);
// 	putchar(out % 10 + '0');
// }
#define cdbg(x...) do { cerr << #x << " -> "; err(x); } while (0)
void err() { cerr << endl; }
template<template<typename...> class T, typename t, typename... A>
void err(T<t> a, A... x) { for (auto v: a) cerr << v << ' '; err(x...); }
template<typename T, typename... A>
void err(T a, A... x) { cerr << a << ' '; err(x...); }


const int N = 3e5 + 5;
const int INF = 1e9;
const int M = 1e7;
const int MOD = 1e9 + 7;


int x,y,p,q;

bool check(int k){
    int gr=floor(1.*(k*(p+q)-x)/(2*x+2*y));
    int gl=ceil(1.*(k*(p+q)-x-y-q)/(2*x+2*y));
    // cdbg(k,gl,gr);
    return (gl<=gr);
}

void solve(){
     x=rd,y=rd,p=rd,q=rd;
    // if(p+q-2*x-2*y==0){
    //     puts("-1");
    //     return ;
    // }
    // int l=ceil(1.*x/(p+q)),r=(x+y+q)/(p+q);
    int ans=INF*INF;
    int l=1,r=INF;
    int res=0;
    // while(l<=r){
    //     int mid=l+r>>1;
    //     if(check(mid))res=mid,r=mid-1;
    //     else l=mid+1;
    // }


    for(int k=res;k<=res+200000;k++){
        int gr=floor(1.*(k*(p+q)-x)/(2*x+2*y));
        int gl=ceil(1.*(k*(p+q)-x-y-q)/(2*x+2*y));
        if((k*(p+q)-x)/(2*x+2*y)==(k*(p+q)-x-y-q)/(2*x+2*y))continue;
        // cdbg(k,gl,gr);
        if(gl<=gr){
            for(int g=gl;g<=gr;g++){
                itn A=k*p+(k-1)*q,B=k*p+k*q,C=(2*g+1)*x+2*g*y,D=(2*g+1)*x+(2*g+1)*y;
                if(max(C,A)<D)ans=min(ans,max(A,C));
            }
            // int g=gl;
        }
    }


    if(ans>=INF*INF)puts("-1"); //!! INF
    else cout<<ans<<endl;
}

signed main() {
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);


    int T=rd;
    while(T--){
        solve();
    }


}