#include
#include
#include
#include
#include
using namespace std;
typedef struct Node
{
int v;
int w;
}bag;
bag b[50];
int total = 0;
void greedySelect(bag b[], int s, int m);
int m = 0;
bool cmp(bag a, bag b)//降序;
{
return a.v > b.v;
}
int main(void)
{
int n;
int s;
scanf("%d", &n);
while(n--)
{
scanf("%d%d", &s, &m);
memset(b, 0, 50 * sizeof(b[0]));
for(int i = 0; i < s; i++)
{
scanf("%d%d", &b[i].v, &b[i].w);
}
sort(b, b + s, cmp);
total = 0;
greedySelect(b, s, m);
printf("%d\n", total);
}
return 0;
}
void greedySelect(bag b[], int s, int m)
{
int c = m;
int i;
for(i = 0; i < s && b[i].w <= c; i++)
{
total += b[i].w * b[i].v;
c -= b[i].w;
}
if(i < s)//将第i个物品的一部分装入包中;
{
total += c * b[i].v;
}
}