#include <iostream>
using namespace std;
int main() {
int n;
cin>>n;
while(n--)
{
int N, K, d[10][10];
cin>>N>>K;
for(int i =0;i<N;i++)
{
for(int j=0;j<2;j++)
{
cin>>d[i][j];
//cout<<d[i][j]<<' ';
if(j==0)
{
if(d[i][j]>K)
d[i][j] = d[i][j] - K;
}
else
K = K - d[i][j];
i++;
d[i][j] = d[i][j] - K;
}
// cout<<'\n';
}
int sum =0;
for(int i =0;i<N;i++)
{
for(int j =0;j<2;j++)
{
if(j==0)
{
int s =j+1;
d[i][j] = d[i][j] * d[i][s];
sum = sum + d[i][j];
}
}
}
cout<<sum<<'\n';
}
}