#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
int main()
{
  int T;
  cin >> T;
  while (T--)
  {
    ll n, k;
    cin >> n >> k;
    vector<ll> A(n);
    for (size_t i = 0; i < n; i++)
    {
      cin >> A[i];
    }

    ll sum = 0, ma = 0, ok = 0, cnt = 0;
    for (size_t i = 0; i < n; i++)
    {
      if (A[i] % k == 0 && A[i] != 0)
      {
        ok++;
      }
      if (A[i] % k != 0)
      {
        cnt++;
      }
      sum += A[i] % k;
      ma = max(ma, A[i] % k);
    }
    if (sum == 0)
    {
      cout << 0 << '\n';
      continue;
    }
    if (sum % k != 0)
    {
      cout << -1 << '\n';
      continue;
    }
    while ((cnt < k) || (sum / k < ma))
    {
      ok -= 1;
      cnt += 1;
      sum += k;
      ma = max(ma, k);
    }
    if (ok < 0)
    {
      cout << -1 << '\n';
      continue;
    }
    cout << sum / k << '\n';
  }
  return 0;
}
/*
  File : ~/yukicoder/526/D.cpp
  Date : 2025/03/07
  Time : 22:15:56
*/