//code 1
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int N = 10006;
const int X = 100000000 + 6;

ll a[N], b[N];
ll c[N];

int n, k;

ll d[N]; //new horse

bool check(ll mid) {
    for (int i = 1; i <= n; ++i) {
        d[i] = a[i] + b[i] * mid;
    }
    sort(d + 1, d + n + 1); reverse(d + 1, d + n + 1);
    sort(c + 1, c + n + 1); reverse(c + 1, c + n + 1);
    int cnt = 0;
    int j = 1;
    for (int i = 1; i <= n; ++i) {
        if (d[i] > c[j]) {
            ++cnt;
            ++j;
        }
        else {
            while (d[i] <= c[j] && j <= n) {
                ++j;
            }
            if (j > n) break;
            ++cnt;
            ++j;
        }
        if (j > n) break;
    }
    if (cnt >= k) return true;
    else return false;
}

int main () {
    int T; scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &n, &k);
        for (int i = 1; i <= n; ++i) {
            scanf("%lld%lld", &a[i], &b[i]);
        }
        for (int i = 1; i <= n; ++i) {
            scanf("%lld", &c[i]);
        }
        int L = -1, R = X;
        //todo: binary search
        while (R - L > 1) {
            int mid = (L + R) / 2;
            if (check(mid)) R = mid;
            else L = mid;
        }
        if (R == X) R = -1;
        printf("%d\n", R);
    }
}

//code 2
#include <bits/stdc++.h>
using namespace std;

int main () {
    multiset<int> st;
    st.insert(1);
    cout << st.size() << endl;
    cout << st.empty() << endl;
    st.insert(1);
    cout << st.size() << endl;
    set<int>::iterator iter = st.find(3);
    if (iter == st.end()) {
        cout << "Not found" << endl;
    }
    else if (iter != st.end()) {
        cout << "Found" << endl;
    }
    st.erase(1);
    st.erase(st.find(1));
}