#include <bits/stdc++.h>
using namespace std;

#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define sz(v) (int)v.size()
#define sq(a) ((a)*(a))

#define MOO(i,a,b) for (int i=a; i<b; i++)
#define M00(i,a) for (int i=0; i<a; i++)
#define MOOd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define M00d(i,a) for (int i = (a)-1; i >= 0; i--)

#define per(i,a,b) for (int i = (b)-1; i >= a; i--)
#define rep(i,a,b) for (int i=a; i<b; i++)

#define FOR(i,a,b) for (int i=a; i<b; i++)
#define F0R(i,a) for (int i=0; i<a; i++)
#define ROF(i,a,b) for (int i = (b)-1; i >= a; i--)
#define R0F(i,a) for (int i = (a)-1; i >= 0; i--)

#define FAST ios::sync_with_stdio(0); cin.tie(0);
#define finish(x) return cout << x << endl, 0;
#define dbg(x) cerr << ">>> " << #x << " = " << x << endl;
#define _ << " _ " <<

#define int long long

template<class T> bool ckmin(T&a, T&b) { bool B = a > b; a = min(a,b); return B; }
template<class T> bool ckmax(T&a, T&b) { bool B = a < b; a = max(a,b); return B; }

typedef long double ld;
typedef pair<int,int> pi;
typedef pair<ld,ld> pld;
typedef complex<ld> cd;

typedef vector<int> vi;
typedef vector<ld> vld;
typedef vector<vector<int>> vvi;

const ld PI = acos(-1.0);
const ld EPS = 1e-7;
const int MOD = 1e9+7;

// Really should be changed to a modular int class 
int POW(int b, int e) {
	int r = 1;
	while(e) {
		if(e % 2 == 1) {
			r *= b;
			r %= MOD;
		}
		e /= 2;
		b *= b;
		b %= MOD;
	}
	return r;
}
int INV(int a) {
	return POW(a, MOD-2);
}
//Constants and Variables here
void solve() {
	int n, m; cin >> n >> m;
	vi diff(n);
	int base = 0;
	M00(i, n) {
		int wn, won;
		cin >> wn >> won;
		base += won;
		diff[i] = wn - won;
	}
	sort(all(diff));
	reverse(all(diff));
	vi pref(n+1);
	M00(i, n) pref[i+1] = pref[i] + diff[i];

	int ans = 0;
	MOO(i, 2, n+1) { // i = number of neighbors
		if(m >= 2 * n - i) {
			ans = max(ans, base + pref[i]);
		}
	}
	if(m >= 2 * n - 1) {
		ans = max(ans, base);
	}
	
	cout << ans << endl;
}

int32_t main() { FAST
	mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	int t; cin >> t;
	while(t--) solve();	
}