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

const int N = 3e5 + 5;
int ar[N], br[N];
void solve() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; ++i)
        cin >> ar[i];
    for (int i = 1; i <= m; ++i)
        cin >> br[i];

    int k = n - m;
    multiset<int> a, b;
    for (int i = 1; i <= n; ++i)
        a.insert(ar[i]);
    for (int i = 1; i <= m; ++i)
        b.insert(br[i]);

    if (*a.rbegin() > *b.rbegin()) {
        cout << "-1\n";
        return;
    }

    sort(ar + 1, ar + 1 + n);
    sort(br + 1, br + 1 + m);
    int sum = 0;
    vector<int> que;
    for (int i = 1; i <= m; ++i) {
        sum += -ar[n + 1 - i] + br[i];
        que.emplace_back(ar[n + 1 - i]);
    }
    sort(que.begin(), que.end());

    // cout << "sum:" << sum << ' ' << k << '\n'; // ft.
    if (sum < 0) {
        cout << "-1\n";
        return;
    }

    vector<int> op;
    // cout << "sum:" << sum << ' ' << k << '\n'; // ft.
    if (sum > k) {
        cout << "-1\n";
        return;
    }

    int bm = *b.begin();
    sum = k - sum;
    while (sum--) {
        int t = *a.begin();
        a.extract(t);
        op.emplace_back(t);
        a.insert(t + 1);
        if (t + 1 > bm) {
            cout << "-1\n";
            return;
        }
        a.extract(*a.begin());
    }

    while (b.size()) {
        while (a.find(*b.begin()) == a.end()) {
            int t = *b.begin();
            auto acc = a.upper_bound(t);
            if (acc == a.begin()) {
                cout << "-1\n";
                return;
            }
            --acc;

            a.extract(*acc);
            op.emplace_back(*acc);
            a.insert((*acc) + 1);
            a.extract(*a.begin());
        }
        a.extract(*b.begin());
        b.extract(*b.begin());
    }
    if (op.size() < n - m) {
        int cnt = n - m - (int)op.size();
        while (cnt--) {
            int t = *a.begin();
            a.extract(t);
            op.emplace_back(t);
            a.insert(t + 1);
            if (t + 1 > bm) {
                cout << "-1\n";
                return;
            }
            a.extract(*a.begin());
        }
    }

    cout << op.size() << '\n';
    for (auto &it : op) {
        cout << it << ' ';
    }
    cout << '\n';
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n;
    cin >> n;
    while (n--)
        solve();
    return 0;
}