#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void solve(){
	int n;
	std::cin >> n;
	std::vector<int> a(n), b(n), idx(n);
	for(int i = 0; i < n; i++) std::cin >> a[i] >> b[i];
	for(int i = 0; i < n; i++) idx[i] = i;
	std::sort(idx.begin(), idx.end(), [&](int x, int y) {return a[x] < a[y];});
	ll sum = 0;
	for(auto e : b) sum += e;
	sum /= 2;
	ll ans = 0;
	ll x = 0;
	for(int i = 0; i < n; i++) {
		if(x + b[idx[i]] <= sum) {
			ans -= a[idx[i]] * b[idx[i]];
			x += b[idx[i]];
		}
		else if(x <= sum) {
			ans -= a[idx[i]] * (sum - x);
			break;
		}
	}
	x = 0;
	
	for(int i = n - 1; i >= 0; i--) {
		if(x + b[idx[i]] <= sum) {
			ans += a[idx[i]] * b[idx[i]];
			x += b[idx[i]];
		}
		else if(x <= sum) {
			ans += a[idx[i]] * (sum - x);
			break;
		}
	}
	
	std::cout << ans << '\n';
}
int main()
{
	int t = 1;
	std::cin >> t;
	while(t--) solve();
}