#include <bits/stdc++.h>

using namespace std;

const int N = 5e5 + 5, L = 1e9;

int n, m, a[N], b[N];
long long mx[1 << 20], lz[1 << 20], rm[1 << 20];
vector<int> lsh;

void build(int k, int l, int r) {
    mx[k] = -1e18, lz[k] = 0, rm[k] = lsh[r - 1];
    if (l == r) return;
    int mid = (l + r) >> 1;
    build(k << 1, l, mid);
    build(k << 1 | 1, mid + 1, r);
}

void pushdown(int k) {
    if (!lz[k]) return;
    mx[k << 1] += lz[k], mx[k << 1 | 1] += lz[k];
    lz[k << 1] += lz[k], lz[k << 1 | 1] += lz[k];
    lz[k] = 0;
}

long long query1(int k, int l, int r, int x, int y, long long cur = -1e18) {
    if (l > x || mx[k] - 1ll * (y - rm[k]) * m <= cur) return -1e18;
    if (l == r) return mx[k] - 1ll * (y - rm[k]) * m;
    pushdown(k);
    int mid = (l + r) >> 1;
    cur = max(cur, query1(k << 1 | 1, mid + 1, r, x, y, cur));
    cur = max(cur, query1(k << 1, l, mid, x, y, cur));
    return cur;
}

long long query2(int k, int l, int r, int x) {
    if (r < x) return -1e18;
    if (l >= x) return mx[k];
    pushdown(k);
    int mid = (l + r) >> 1;
    return max(query2(k << 1, l, mid, x), query2(k << 1 | 1, mid + 1, r, x));
}

void modify(int k, int l, int r, int x, long long y) {
    if (l == r) {
        mx[k] = max(mx[k], y);
        return;
    }
    pushdown(k);
    int mid = (l + r) >> 1;
    if (x <= mid) modify(k << 1, l, mid, x, y);
    else modify(k << 1 | 1, mid + 1, r, x, y);
    mx[k] = max(mx[k << 1], mx[k << 1 | 1]);
}

void add(int k, int l, int r, int x, int y) {
    if (r < x) return;
    if (l >= x) {
        mx[k] += y, lz[k] += y;
        return;
    }
    pushdown(k);
    int mid = (l + r) >> 1;
    add(k << 1, l, mid, x, y), add(k << 1 | 1, mid + 1, r, x, y);
    mx[k] = max(mx[k << 1], mx[k << 1 | 1]);
}

int main() {
    int T; scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &n, &m);
        lsh = {0};
        for (int i = 1; i <= n; i++) {
            scanf("%d%d", &a[i], &b[i]);
            if (b[i] > 0) lsh.push_back(a[i]);
            else lsh.push_back(a[i] - 1);
        }
        sort(lsh.begin(), lsh.end());
        lsh.erase(unique(lsh.begin(), lsh.end()), lsh.end());
        build(1, 1, lsh.size());
        auto getId = [&](int x) {
            return lower_bound(lsh.begin(), lsh.end(), x) - lsh.begin() + 1;
        };
        modify(1, 1, lsh.size(), getId(0), 0);
        for (int i = 1; i <= n; i++) {
            if (b[i] > 0) {
                modify(1, 1, lsh.size(), getId(a[i]), query1(1, 1, lsh.size(), getId(a[i]), a[i]));
            } else {
                modify(1, 1, lsh.size(), getId(a[i] - 1), query2(1, 1, lsh.size(), getId(a[i] - 1)));
            }
            add(1, 1, lsh.size(), getId(a[i]), b[i]);
        }
        printf("%lld\n", mx[1]);
    }
    return 0;
}