#include <iostream>
#include <bits/stdc++.h>
using namespace std;
 
int main() {
	// your code goes here
	int t;cin>>t;
	while(t--){
	int n,m;cin>>n>>m;
	int count=0;
	vector <pair<int,int>> arr(n);
	for(int i=0;i<n;i++) {cin>>arr[i].first;
		arr[i].second=i+1;
	}
	sort(arr.begin(),arr.end());
	if(m<n) cout<<"-1"<<endl;
	else{
		int tep=m;
		for(int i=0;i<n-1;i++){
			count=count+(arr[i].first+arr[i+1].first);
		//	cout<<i+1<<" "<<i+2<<endl;
			m--;
		}
		count=count+(arr[0].first+arr[n-1].first);
		//cout<<1<<" "<<n-1<<endl;
		m--;
		//cout<<count<<endl;
		if(m>0){
			count=count+(m*(arr[0].first+arr[1].first));
		//	cout<<1<<" "<<2<<endl;
		}
		cout<<count<<endl;
		for(int i=0;i<n-1;i++){
		//	count=count+(arr[i].first+arr[i+1].first);
			cout<<arr[i].second<<" "<<arr[i+1].second<<endl;
			tep--;
		}
		//count=count+(arr[0].first+arr[n-1].first);
		cout<<arr[0].second<<" "<<arr[n-1].second<<endl;
		tep--;
		//cout<<count<<endl;
		while(tep>0){
		//	count=count+(m*(arr[0].first+arr[1].first));
			tep--;
			cout<<arr[0].second<<" "<<arr[1].second<<endl;
		}
	}
	}
	return 0;
}

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Mwo0IDYKMSAxIDEgMQozIDEKMSAyIDMKMyA0CjEgMiAzCg==

3
4 6
1 1 1 1
3 1
1 2 3
3 4
1 2 3