#ifdef LOCAL
//#define _GLIBCXX_DEBUG
#else
    #pragma GCC optimize("O3")
    #pragma GCC optimize("unroll-loops")
    //#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#endif

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<char> Vc;
typedef vector<P> VP;
typedef vector<VP> VVP;
typedef vector<Vec> VV;
typedef vector<Vi> VVi;
typedef vector<Vc> VVc;
typedef vector<VV> VVV;
typedef vector<VVV> VVVV;
#define MAKEVV(variable, a, ...) VV variable(a, Vec(__VA_ARGS__))
#define MAKEVVc(variable, a, ...) VVc variable(a,Vc(__VA_ARGS__))
#define MAKEVVV(variable, a, b, ...) VVV variable(a, VV(b, Vec(__VA_ARGS__)))
#define MAKEVVVV(variable, a, b, c, ...) VVVV variable(a, VVV(b, (VV(c, Vec(__VA_ARGS__)))))

#define endl '\n'
#define REP(i, a, b) for(ll i=(a); i<(b); i++)
#define PER(i, a, b) for(ll i=(a); i>=(b); i--)
#define rep(i, n) REP(i, 0, n)
#define per(i, n) PER(i, n, 0)
const ll INF = 4'000'000'000'000'000'010LL;
const ll MOD=998244353;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define YES(n) cout << ((n) ? "YES" : "NO") << endl;
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a,b)
#define Each(a,b) for(auto &a :b)
#define rEach(i, mp) for (auto i = mp.rbegin(); i != mp.rend(); ++i)
#define SUM(a) accumulate(ALL(a),0LL)
#ifdef LOCAL
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define dbgmap(mp) cerr << #mp << ":"<<endl; for (auto i = mp.begin(); i != mp.end(); ++i) { cerr << i->first <<":"<<i->second << endl;}
#define dbgset(st) cerr << #st << ":"<<endl; for (auto i = st.begin(); i != st.end(); ++i) { cerr << *i <<" ";}cerr<<endl;
#define dbgarr(n,m,arr) rep(iii,n){rep(jjj,m){cerr<<arr[iii][jjj]<<" ";}cerr<<endl;}
#define dbgdp(n,arr) rep(iii,n){cerr<<arr[iii]<<" ";}cerr<<endl;
#else
#define dbg(...)
#define dbgmap(...)
#define dbgset(...)
#define dbgarr(...)
#define dbgdp(...)
#endif
#define out(a) cout<<a<<endl
#define outminusone(a) cout<< ( a==INF ? -1 : a ) <<endl
#define out2(a,b) cout<<a<<" "<<b<<endl
#define vout(v) rep(i,v.size()){cout<<v[i]<<" ";}cout<<endl
#define Uniq(v) v.erase(unique(v.begin(), v.end()), v.end())
#define fi first
#define se second

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
template<class T>auto lb(T &X, ll x){return lower_bound(ALL(X),x) - X.begin();}
template<class T>auto ub(T &X, ll x){return upper_bound(ALL(X),x) - X.begin();}
ll popcnt(ll x){return __builtin_popcount(x);}
ll topbit(ll t){return t==0?-1:63-__builtin_clzll(t);}
ll floor(ll y,ll x){assert(x != 0);if(x < 0){y *= -1; x *= -1;}if(y < 0){return (y-x+1)/x;}return y/x;};
ll ceil(ll y, ll x){assert(x != 0);if(x < 0){y *= -1; x *= -1;}if(y < 0){return y/x;}return (y+x-1)/x;};

template<typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) { return s<<"("<<p.first<<", "<<p.second<<")"; }

template<typename T1, typename T2>
istream &operator>>(istream &i, pair<T1, T2> &p) { return i>>p.first>>p.second; }

template<typename T>istream& operator>>(istream&i,vector<T>&v)
{rep(j,v.size())i>>v[j];return i;}

// vector
template<typename T>
ostream &operator<<(ostream &s, const vector<T> &v) {
    int len=v.size();
    for(int i=0; i<len; ++i) {
        s<<v[i];
        if(i<len-1) s<<"	";
    }
    return s;
}

// 2 dimentional vector
template<typename T>
ostream &operator<<(ostream &s, const vector<vector<T> > &vv) {
    s<<endl;
    int len=vv.size();
    for(int i=0; i<len; ++i) {
        s<<vv[i]<<endl;
    }
    return s;
}

int solve(){
    ll L,R,A,B;
    cin>>L>>R>>A>>B;
    ll mi = INF;
    ll ma = -INF;
    chmin(mi,A*L+B);
    chmin(mi,A*R+B);
    chmax(ma,A*L+B);
    chmax(ma,A*R+B);
    out(ma);
    return  0;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout<<std::setprecision(20);
    ll T;
    cin>>T;
    while(T--)
    solve();
}