#include <bits/stdc++.h>
using namespace std;
long long dx[] = {1, -1, 0, 0};
long long dy[] = {0, 0, 1, -1};
const long long inf = 1e18 + 5;
const long long sz = 2e5 + 5, mod = 998244353;
long long t, n, m, k, q;
long long power(long long a, long long b) {
  long long ans = 1;
  while (b > 0) {
    if (b & 1) {
      ans = (ans * a) % mod;
    }
    a = (a * a) % mod;
    b >>= 1;
  }
  return ans;
}
long long Inv(long long a) { return power(a, mod - 2); }
vector<vector<long long> > gr(sz);
vector<long long> level(sz, 0);
map<long long, long long> mp;
vector<long long> child(sz, 0);
long long DFS1(long long s, long long p, long long lev) {
  level[s] = lev;
  long long ans = 1;
  for (auto i : gr[s]) {
    if (i != p) ans += DFS1(i, s, lev + 1);
  }
  child[s] = ans;
  return ans;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  t = 1;
  cin >> t;
  while (t--) {
    cin >> n >> k;
    vector<long long> v(n);
    for (auto &i : v) cin >> i;
    sort(v.begin(), v.end());
    if (k == 0) {
      cout << v[0] << "\n";
      continue;
    }
    long long l = 0, r = k;
    long long mn = v[r] - v[l];
    for (long long i = k; i < n; i++) {
      if (v[i] - v[i - k] < mn) {
        l = i - k;
        r = i;
        mn = v[i] - v[i - k];
      }
    }
    cout << (v[l] + v[r]) / 2 << "\n";
  }
  return 0;
}
