#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

template <class T>
long long max_distinct_k(vector<T> a, int k) {
  const int n = a.size();
  if (n < k) return 0;
  sort(a.begin(), a.end());
  const int base = n - k;
  long long rest = accumulate(a.begin(), a.begin() + base, 0LL);
  for (int i = base + 1; i < n; i++) {
    long long mx = rest / (i - base);
    if (mx < a[i] - a[i - 1]) {
      return a[i - 1] + mx;
    }
    rest -= (a[i] - a[i - 1]) * (i - base);
  }
  return a[n - 1] + rest / k;
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt;
  cin >> tt;
  while (tt--) {
    int n, k;
    cin >> n >> k;
    vector<pair<ll, ll>> ar(n);
    for (auto& [ai, ri] : ar) {
      cin >> ai;
      ri = ai % k;
      ai -= ri;
    }
    ranges::sort(ar, {}, &pair<ll, ll>::second);
    ll sm = 0, mx = 0;
    for (auto [ai, ri] : ar) {
      sm += ri;
      mx = ri;
    }
    ll ans = [&]() {
      int p = 0;
      rep(_, (3*n + 4) * (3*n + 4)) {
        if (sm % k == 0 && mx <= sm / k) return sm / k;
        while (!ar.empty() && ar[p].first < k) {
          ar.erase(ar.begin() + p);
          if (p == ssize(ar)) p = 0;
        }
        if (ar.empty()) break;
        auto& [ap, rp] = ar[p];
        ap -= k;
        rp += k;
        sm += k;
        mx = rp;
        p++;
        if (p == ssize(ar)) p = 0;
      }
      return -1LL;
    }();
    cout << ans << '\n';
  }
}