#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
void debug_(const char *s, auto ...a) {
  cerr << "\e[1;32m(" << s << ") = (";
  int f = 0;
  (..., (cerr << (f++ ? ", " : "") << a));
  cerr << ")\e[0m\n";
}
void orange_(const char *s, auto L, auto R) {
  cerr << "\e[1;33m[ " << s << " ] = [ ";
  for (int f = 0; L != R; L++)
    cerr << (f++ ? ", " : "") << *L;
  cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

void solve() {
  int n, m;
  cin >> n >> m;
  vector<int> a(n), b(m);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 0; i < m; i++) {
    cin >> b[i];
  }
  sort(all(a), greater<>());
  sort(all(b), greater<>());

  if (n < m) {
    cout << -1 << '\n';
    return;
  }

  int64_t tot = 0;
  for (int i = 0; i < m; i++) {
    if (b[i] < a[i]) {
      cout << -1 << '\n';
      return;
    }
    tot += b[i] - a[i];
  }
  if (tot > n - m) {
    cout << -1 << '\n';
    return;
  }

  int rest = (n - m) - tot;

  set<pair<int,int>, greater<>> z;
  for (int i = 0; i < m; i++) {
    int cur = b[i] - a[i];
    if (cur)
      z.emplace(b[i], i);
  }

  multiset<int> ms_b(all(b));

  vector<int> ans;
  for (int it = 0; it < n - m; it++) {
    int toadd = a[it + m] + rest;
    toadd = min(*ms_b.begin(), toadd);
    if (toadd < a[it + m]) {
      cout << -1 << '\n';
      return;
    }
    int k = toadd - a[it + m];
    rest -= k;
    if (k) {
      z.emplace(toadd, it + m);
    }

    b.push_back(toadd);
    ms_b.insert(toadd);

    if (z.empty()) {
      cout << -1 << '\n';
      return;
    }
    auto [val, i] = *z.begin();
    z.erase(z.begin());

    assert (b[i] == val);
    ms_b.erase(ms_b.find(b[i]));
    b[i] -= 1;
    ms_b.insert(b[i]);

    if (b[i] > a[i])
      z.emplace(b[i], i);
    ans.push_back(b[i]);
  }

  reverse(all(ans));
  cout << ans.size() << '\n';
  for (size_t i = 0; i < ans.size(); i++) {
    cout << ans[i] << (i+1==ans.size() ? '\n' : ' ');
  }


}

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--)
    solve();

  return 0;
}