#include<stdio.h>
#include<stdlib.h>
struct Node
{
    double value;
    double weight;
}a[10];

void quick_sort(struct Node *arr, int l, int r)  //对结束时间进行排序
{
    if (l < r)     //进行判断，用来终止递归
    {
        int i = l, j = r, x = arr[l].value;
        struct Node temp = arr[l];          //用来交换结构体数组变量
        while (i < j)
        {
            while (i < j && x <= arr[j].value)    //从右往左找一个小于x的数
                j--;
            if (i < j)
                arr[i++] = arr[j];
            while (i < j && x > arr[i].value)     //从左往右找一个大于x的数
                i++;
            if (i < j)
                arr[j--]= arr[i];
        }
        arr[i] = temp;
        quick_sort(arr, l ,i - 1);              //递归调用，分治思想，左边分治。
        quick_sort(arr, i + 1, r);              //右边分治
    }
}

int main()
{
    int s, i, j;
    scanf("%d",&s);
    while (s--)             //s组测试数据
    {
        int n;
        double m, total_value = 0, total_weight = 0;           //m为背包所能装的最大重量
        scanf("%d%lf",&n, &m);
        for (i = 0; i < n; i++)
            scanf("%lf%lf",&a[i].value, &a[i].weight);
        quick_sort(a, 0, n - 1);
        for (i = n - 1; i >= 0; i--)
        {
            if (total_weight + a[i].weight <= m)
            {
                total_weight += a[i].weight;
                total_value += a[i].value * a[i].weight;
            }
            else
                break;
        }
        total_value += (m - total_weight) * a[i].value;
        printf("%d\n",(int)total_value);
    }
    return 0;
}