#include<bits/stdc++.h>
using namespace std;
int const maxn = 5e5+10;
#define int long long

int dp[maxn*2];
int a[maxn],b[maxn];

signed main(){
	int t;
	cin >> t ;
	while(t--){
		int n,m;
		cin >> n >> m ;
		for(int i = 1;i <= n;i ++){
			cin >>a[i] >> b[i];
		}
		memset(dp,0,sizeof dp);
		int j ,i;
		i = 1;
		for( j = 1;j <= m&&i <= n;j ++){
			dp[j] = max(dp[j-1] + a[i],dp[max(j-2,0ll)] + b[i]);
			i++;
		}
		cout <<max(dp[j-1] ,dp[max(j-2,0ll)] )<<'\n';
	}
	
	return 0;
}