#include <cstdio>

int main() {
    int Tests;
    scanf("%d", &Tests);
    while (Tests--) {
        int N, M, Ans = 0x3f3f3f3f;
        scanf("%d%d", &N, &M);
        for (int i = 1; i <= N; ++i) {
            int x, y;
            scanf("%d%d", &x, &y);
            int z = (M + x - 1) / x * y;
            Ans = Ans < z ? Ans : z;
        }
        printf("%d\n", Ans);
    }
    return 0;
}