#include <bits/stdc++.h>
using namespace std;
int64_t mod = 1e9 + 7;
int64_t mod1 = 1e9 + 5;
int64_t power(int64_t a, int64_t b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0)
    return power(((((a) % mod) * ((a) % mod)) % mod), b / 2) % mod;
  else
    return (((a) % mod) *
            (power(((((a) % mod) * ((a) % mod)) % mod), b / 2) % mod)) %
           mod;
}
inline int64_t inverse(int64_t a, int64_t md) {
  a %= md;
  if (a < 0) a += md;
  int64_t b = md, u = 0, v = 1;
  while (a) {
    int64_t t = b / a;
    b -= t * a;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  assert(b == 1);
  if (u < 0) u += md;
  return u;
}
const int64_t ce = 1e9 + 7;
int64_t fast_mod(int64_t input) { return input < ce ? input : input % ce; }
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int64_t t;
  cin >> t;
  while (t--) {
    int64_t n, k;
    cin >> n >> k;
    pair<int64_t, int64_t> a[2];
    cin >> a[0].first >> a[0].second >> a[1].first >> a[1].second;
    sort(a, a + 2);
    int64_t in = 0;
    for (int64_t i = 1; i <= n; i++) {
      if (a[1].first <= a[0].second) {
        in += min(a[1].second - a[1].first, a[0].second - a[1].first);
      }
    }
    if (in >= k) {
      cout << 0 << '\n';
      continue;
    }
    int64_t ti = 0;
    int64_t indi = in / n;
    int64_t indi_t = 0;
    if (a[1].first > a[0].second) {
      ti += (a[1].first - a[0].second);
      indi_t = ti;
    }
    int64_t len = max(a[1].second - a[0].first, a[0].second - a[0].first);
    if (len - indi + in >= k) {
      cout << ti + (k - in) << '\n';
      continue;
    }
    ti += len - in / n;
    in += len - indi;
    if (indi != 0) {
      for (int64_t i = 2; i <= n; i++) {
        if (in + len - indi >= k) {
          ti += k - in;
          in = k;
          break;
        } else {
          ti += len - indi;
          in += len - indi;
        }
      }
      if (in == k)
        cout << ti << '\n';
      else {
        cout << ti + (k - in) * 2 << '\n';
      }
      continue;
    } else {
      for (int64_t i = 2; i <= n; i++) {
        if (in + len >= k) {
          ti += min(2 * (k - in), indi_t + k - in);
          in = k;
          break;
        } else {
          ti += min(2 * len, indi_t + len);
          in += len;
        }
      }
      if (in == k)
        cout << ti << '\n';
      else {
        cout << ti + (k - in) * 2 << '\n';
      }
      continue;
    }
  }
}
