#include using namespace std ; #define fast_input_output ios::sync_with_stdio(false); cin.tie(nullptr); // #pragma GCC target("avx2") // #pragma GCC optimize("O3") #pragma GCC target("avx") #pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") typedef long long ll ; typedef long double ld ; typedef pair P ; typedef tuple TP ; #define chmin(a,b) a = min(a,b) #define chmax(a,b) a = max(a,b) #define bit_count(x) __builtin_popcountll(x) #define gcd(a,b) __gcd(a,b) #define lcm(a,b) a / gcd(a,b) * b #define rep(i,n) for(int i = 0 ; i < n ; i++) #define rrep(i,a,b) for(int i = a ; i < b ; i++) #define repi(it,S) for(auto it = S.begin() ; it != S.end() ; it++) #define pt(a) cout << a << endl #define DEBUG(...) ; cout << #__VA_ARGS__ << endl ; for(auto x : {__VA_ARGS__}) cout << x << " " ; cout << endl ; #define DEBUG_LIST(...) cout << #__VA_ARGS__ << endl ; DEBUG_REP(__VA_ARGS__) ; #define DEBUG_REP(V) cout << "{ " ; repi(itr,V) cout << *itr << ", " ; cout << "}" << endl ; #define debug(a) cout << #a << " " << a << endl #define all(a) a.begin(), a.end() #define endl "\n" void solve(){ ll l, r, a, b; cin >> l >> r >> a >> b; ll val = -1e18; rrep(x,l,r+1){ chmax(val, a*x+b); } cout << val << endl; } int main(){ fast_input_output int t; cin >> t; rep(i,t) solve(); }