#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  cin >> t;
  while (t--) {
    long long int n, k;
    cin >> n >> k;
    long long int a, b, c, d;
    cin >> a >> b;
    cin >> c >> d;
    if (a > c || (a == c && b > d)) {
      swap(a, c);
      swap(b, d);
    }
    long long int per = max(0LL, c - b);
    long long int capacity = max(b, d) - a;
    long long int current = max(0LL, min(b, d) - c);
    capacity = capacity - current;
    k = max(0LL, k - n * current);
    if (k == 0) {
      cout << 0 << endl;
      continue;
    }
    long long int ans = 0;
    ans += per;
    long long int num = min(k, capacity);
    ans += num;
    k -= num;
    n--;
    if (k == 0) {
      cout << ans << endl;
      continue;
    }
    if (per + capacity >= 2 * capacity) {
      ans += 2 * k;
    } else {
      long long int divi = min(k / capacity, n);
      ans += (per + capacity) * (divi);
      k -= divi * capacity;
      if (divi == n || k >= capacity) {
        ans += 2 * k;
      } else {
        if (k + per < 2 * k)
          ans += k + per;
        else
          ans += 2 * k;
      }
    }
    cout << ans << endl;
  }
  return 0;
}
