#include <bits/stdc++.h>
using std::bitset;
using std::cout;
using std::deque;
using std::endl;
using std::greater;
using std::lower_bound;
using std::make_pair;
using std::map;
using std::max;
using std::min;
using std::multimap;
using std::multiset;
using std::nth_element;
using std::pair;
using std::priority_queue;
using std::queue;
using std::reverse; 
using std::set;
using std::sort;
using std::sqrt;
using std::stable_sort;
using std::string;
using std::swap;
using std::unique;
using std::upper_bound;
using std::vector;
typedef long long li;
typedef __int128 ll;
typedef long double lf; 

inline li read(){
	long long ans = 0, f = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9'){
		f = (ch == '-') ? -1 : 1;
		ch = getchar();
	}
	while(ch <= '9' && ch >= '0'){
		ans = ans * 10 + (ch ^ 48);
		ch = getchar();
	}
	return ans * f;
} 

li n, k, X, Y, A;
const li inf = 9e18;
li x[200010], y[200010], a[200010], sumx[200010], sumy[200010];

pair<li, li> calc(li op1, li op2, li op3, li op4, li p, li debug = 0){
	li P = op1 * sumx[p] + op2 * sumy[p] + X * op3 + Y * op4 - p * k;
	li K = op1 * sumx[n] + op2 * sumy[n] - n * k;
	K = -K, P = -P;
	// if(debug) cout << K << " " << P << endl;
	// cout << K << "x + " << P << endl;
	if(K < 0){
		if(P < 0) return {inf, 0};
		return {0, -P / K};
	} else if(K == 0){
		if(P < 0) return {inf, 0};
		return {0, inf};
	} else if(K > 0){
		return {max(0ll, (-P + K - 1) / K), inf};
	}
	printf("E.Space\n");
	assert(1 < 0);
}

pair<li, li> work(pair<li, li> x, pair<li, li> y){
	if(x.first > x.second || y.first > y.second) return {inf, 0};
	if(x > y) swap(x, y);
	if(x.second < y.first) return {inf, 0};
	return {y.first, x.second};
}

int main(){
    // freopen("wonderful.ans", "r", stdin);
    // freopen("www.ww", "w", stdout);
    // freopen("wind.in", "r", stdin);
    // freopen("wind.out", "w", stdout);
	li T = read();
	while(T--){
		n = read(), k = read(), X = read(), Y = read();
		for(li i = 1; i <= n; i++){
			x[i] = read(), y[i] = read();
			sumx[i] = x[i] + sumx[i - 1], sumy[i] = y[i] + sumy[i - 1];
		}
		li minn = inf;
		for(li p = 0; p < n; p++){
			// cout << "p = " << p << endl;
			auto p1 = calc(1, 1, -1, -1, p);
			// cout << p1.first << " " << p1.second << endl;
			auto p2 = calc(1, -1, -1, 1, p);
			// cout << p2.first << " " << p2.second << endl;
			auto p3 = calc(-1, 1, 1, -1, p);
			// cout << p3.first << " " << p3.second << endl;
			auto p4 = calc(-1, -1, 1, 1, p);
			// cout << p4.first << " " << p4.second << endl;
			p1 = work(p1, p2);
			p1 = work(p1, p3);
			p1 = work(p1, p4);
			if(p1.first <= p1.second){
				// if(n * p1.first + p == 5864491400){
				// 	printf("??? %lld %lld p = %lld\n", p1.first, p1.second, p);
				// 	{
				// 		auto p1 = calc(1, 1, -1, -1, p, 1);
				// 		cout << p1.first << " " << p1.second << endl;
				// 		auto p2 = calc(1, -1, -1, 1, p);
				// 		cout << p2.first << " " << p2.second << endl;
				// 		auto p3 = calc(-1, 1, 1, -1, p);
				// 		cout << p3.first << " " << p3.second << endl;
				// 		auto p4 = calc(-1, -1, 1, 1, p, 1);
				// 		cout << p4.first << " " << p4.second << endl;	
				// 	}
				// }
				minn = min(minn, n * p1.first + p);
			}
			// cout << p << " " << p1.first << " " << p1.second << endl;
		}
		if(minn == inf) minn = -1;
		printf("%lld\n", minn); 
	}	
    return 0;
}