#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

template<class Type>
inline void R(Type &x) {
    int c = getchar();
    bool neg = 0;
    for (; c < 48 || c > 57; c = getchar())if (c == '-')neg = true;
    for (x = 0; c > 47 && c < 58; x = (Type) 10 * x + c - 48, c = getchar());
    if (neg)x = -x;
}

const int INF = 0x3f3f3f3f;

int T, n, m, x[101], y[101];

int main() {
    R(T);
    while (T--) {
        int ans = INF;
        R(n);
        R(m);
        for (int i = 1; i <= n; ++i) {
            R(x[i]);
            R(y[i]);
            int tmp = m / x[i];
            if (m % x[i])
                ans = min(ans, (tmp + 1) * y[i]);
            else
                ans = min(ans, tmp * y[i]);
        }
        printf("%d\n", ans);
    }
    return 0;
}