#include <bits/stdc++.h>
using namespace std;
void solve(){
	int n,m,cnt=0;
	cin>>n>>m;
	vector<int> ans,a(n),b(m);
	for(int&x:a) cin>>x;
	for(int&x:b) cin>>x;
	sort(a.rbegin(),a.rend());
	sort(b.rbegin(),b.rend());
	for(int i=0;i<m;i++){
		if(a[i]>b[i]){
			cout<<"-1\n";
			return;
		}
		cnt+=b[i]-a[i];
		if(n-cnt<m){
			cout<<"-1\n";
			return;
		}
	}
	multiset<int> s(begin(a),end(a)),h(begin(b),end(b));
	for(int t=n-m-cnt;t--;){
		int x=*s.begin();
		s.erase(s.begin());
		ans.push_back(x);
		s.insert(x+1);
		s.erase(s.begin());
	}
	for(int i=0;i<m;i++) while(a[i]<b[i]){
		auto it=s.find(a[i]);
		ans.push_back(a[i]);
		if(it==end(s)){
			cout<<"-1\n";
			return;
		}
		s.erase(it);
		s.insert(++a[i]);
		s.erase(s.begin());
	}
	if(s!=h) cout<<"-1\n";
	else{
		cout<<n-m<<"\n";
		for(int x:ans) cout<<x<<" ";
		cout<<"\n";
	}
}
int main(){
	cin.tie(0)->sync_with_stdio(0);
	int t;
	cin>>t;
	while(t--) solve();
	return 0;
}