{

public static void main( String[] args )

{

Scanner s = new Scanner(System.in);

int t = s.nextInt();

while(t-->0)

{

int n= s.nextInt();

int m = s.nextInt();

int sum=0;

List<Vertex> a = new ArrayList<Vertex>();

for(int i=0;i<n;i++)

{

Vertex v= new Vertex();

v.weight = s.nextInt();

v.index = i+1;

sum+=v.weight;

a.add( v );

}

Collections.sort( a,(o1,o2)->o1.weight-o2.weight );

if(n<=2 || n>m)

{

System.out.println( -1 );

continue;

}

else

{

int sumOfTwoWeights = a.get( 0 ).weight+a.get(1).weight;

int minCost = 2*(sum)+(m-n)*sumOfTwoWeights;

System.out.println( minCost );

for(int i=1;i<n;i++)

System.out.println( a.get( i-1 ).index+" "+a.get( i ).index );

System.out.println( a.get( 0 ).index+" "+a.get( n-1 ).index );

for(int i=0;i<m-n;i++)

System.out.println( a.get( 0 ).index+" "+a.get( 1 ).index );

}

}

}

{

int index;

int weight;

}