#include<bits/stdc++.h>
#define ll long long
#define all(x) x.begin(), x.end()
#define lowbit(i) ((i)&(-i))
#define pii pair<int,int>
#define endl '\n'
#define mk(x,y) make_pair(x,y)
#define popcount(x) __builtin_popcount(x)
#define LF(x) fixed<<setprecision(x)
const double pi=3.14159265358979323846;
const double eps=1e-9;
const int inf=1e9;
const long long INF=4e18;
const int mod=1e9+7;
using namespace std;
const int N=1e5+10;
struct val
{
	ll a,b;
};
void solve()
{
	int n,m;
	cin>>n>>m;
	vector<val>x(n+1);
	for(int i=1;i<=n;i++){
		cin>>x[i].a>>x[i].b;
	}
	sort(x.begin()+1,x.end(),[&](val t1,val t2){
		return t1.b-t1.a<t2.b-t2.a;
	});
	reverse(x.begin()+1,x.end());
	vector<ll>sum1(n+1,0),sum2(n+1,0);
	for(int i=1;i<=n;i++){
		sum1[i]=sum1[i-1]+x[i].b;
		sum2[i]=sum2[i-1]+x[i].a;
		// cout<<x[i].a<<" "<<x[i].b<<endl;
	}
	ll ans=0;
	for(int i=0;i<=n;i++){//枚举没有邻居的个数
		if((n-i>=2&&n+i<=m)||(n==i&&2*n-1<=m)){
			ll res=sum1[i];
			res+=sum2[n]-sum2[i];
			ans=max(ans,res);
		}
	}
	cout<<ans<<endl;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    int T=1;
    cin>>T;
    while(T--){
        solve();
    }
    return 0;
}