#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  long long int a, b, c, r;
  while (t--) {
    long long int ans = 0, mx = 0, mn = 0;
    cin >> a >> b >> c >> r;
    if (a >= b) {
      mx = a;
      mn = b;
    } else {
      mx = b;
      mn = a;
    }
    if (c == mx || c == mn) {
      ans = mx - mn - r;
      if (ans < 0) ans = 0;
      cout << ans << endl;
    } else if (c > mn && c < mx) {
      if (abs(c - mn) < r)
        ans = mx - mn - (r + abs(c - mn));
      else if (abs(mx - c) < r)
        ans = mx - mn - (r + abs(mx - c));
      else
        ans = mx - mn - 2 * r;
      if (ans < 0) ans = 0;
      cout << ans << endl;
    } else {
      if (mn > c && abs(mn - c) < r)
        ans = mx - mn - (r - abs(mn - c));
      else if (c > mx && abs(c - mx) < r)
        ans = mx - mn - (r - abs(c - mx));
      else
        ans = mx - mn;
      if (ans < 0) ans = 0;
      cout << ans << endl;
    }
  }
  return 0;
}
