#include<cstdio>
#include<cassert>
#include<vector>
#include<iostream>
#include<string>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<functional>
#include<utility>
#include<cstring>
#include<numeric>
#include<algorithm>
#include<atcoder/math>
#include<atcoder/modint>
#include<ext/pb_ds/assoc_container.hpp>
//#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using Mint = modint998244353;
using mint = modint;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define rep2(i, a, b) for (int i = (int)a; i < (int)(b); ++i)
#define rrep2(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); --i)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr int dx[] = {-1,0,1,0};
constexpr int dy[] = {0,-1,0,1};
constexpr int MAX_N = 100000;
//ダイクストラ法：makedijkstra
//エラトステネスの篩：makesieve
//テストケースが複数の場合：multest

int main(){
    int total_testcases;
    scanf("%d", &total_testcases);
    for (int testcase_i = 1; testcase_i <= total_testcases; ++testcase_i){
        int L, R, A, B;
        scanf("%d %d %d %d", &L, &R, &A, &B);
        printf("%d\n", A*(A > 0 ? R : L) + B);
    }
}