#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
template <class T>
using V = vector<T>;
const ll inf = (1e18);
const ll mod = 1000000007;
ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
ll LCM(ll c, ll d) { return c / GCD(c, d) * d; }
struct __INIT {
  __INIT() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
  }
} __init;
template <class T>
bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
void pitsu() {
  int n, k;
  cin >> n >> k;
  map<ll, ll> mp;
  ll a;
  for (int i = 0; i < n; i++) {
    cin >> a;
    if (a % k == 0) continue;
    mp[k - a % k]++;
  }
  ll d = 0, ans = 0;
  for (auto p : mp) {
    if (chmax(d, p.second)) {
      ans = (p.second - 1) * k + p.first + 1;
    } else if (d == p.second) {
      chmax(ans, (p.second - 1) * k + p.first + 1);
    }
  }
  cout << ans << "\n";
}
int main() {
  int t;
  cin >> t;
  while (t--) pitsu();
}
