revana

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

typedef long long ll;
#define _FastIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define MAXX 1005

int n , a , b , c , r , t;

int main()
{
    cin >> t;
    for(int i = 0; i < t; i++){
        cin >> a >> b >> c >> r;
        int x = c - r;
        int y = c + r;
        if(a > b)
            swap(a , b);
        if(a >= x && a >= y){
            cout << b - a << endl;
            continue;
        }
        if(b <= x && b <= y){
            cout << b - a << endl;
            continue;
        }
        if(a <= x && b >= y){
            cout << b - a - 2 * r << endl;
            continue;
        }
        if(a >= x && b <= y){
            cout << "0" << endl;
            continue;
        }
        if(a <= x && b <= y){
            cout << x - a << endl;
            continue;
        }
        if(a >= x && b >= y){
            cout << b - y << endl;
            continue;
        }
    }
    return 0;
}