#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
void die(string S){puts(S.c_str());exit(0);}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        ll a,b,c,d;
        cin>>a>>b>>c>>d;
        cout<<(min(min(min(c-1,b-d),(a-1+abs(c-d)-min(1ll,abs(c-d)))/2),a-1))*(min(min(min(c-1,b-d),(a-1+abs(c-d)-min(1ll,abs(c-d)))/2),a-1))<<endl;
    }
    return 0;
}