#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
void _print() { cout << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  cout << t;
  if (sizeof...(v)) cout << ", ";
  _print(v...);
}
using ll = long long int;
using ld = long double;
template <typename T, typename V>
using P = pair<T, V>;
template <typename T>
using V = vector<T>;
constexpr ll MOD = 1e9 + 7;
constexpr ll INF = 0x3f3f3f3f;
constexpr ld PI = 3.1415926535897932384626;
constexpr ld EPS = 1e-9;
constexpr ll MAX = 5e5 + 5;
ll power(ll a, ll b, ll mod) {
  ll ans = 1;
  while (b) {
    if (b & 1) (ans *= a) %= mod;
    (a *= a) %= mod, b >>= 1;
  }
  return ans;
}
constexpr ll MOD2 = 999999937;
void solve() {
  ll n, p;
  cin >> n >> p;
  V<ll> v(n);
  for (ll i = (ll)(0); i < (ll)(n); i++) cin >> v[i];
  sort(v.rbegin(), v.rend());
  ll ans = 0, ans2 = 0;
  for (ll i : v) {
    if (ans == 0 && ans2 == 0)
      ans = power(p, i, MOD), ans2 = power(p, i, MOD2);
    else {
      ans = (ans - power(p, i, MOD) + MOD) % MOD;
      ans2 = (ans2 - power(p, i, MOD2) + MOD2) % MOD2;
    }
  }
  cout << ans << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ll t;
  cin >> t;
  while (t--) solve();
}
