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

const int N = 100005; 
const long long INF = 1e18;
int n, m;
int a[N], b[N];
long long mx[N * 4], lz[N * 4], rm[N * 4];
vector<int> lsh;

void build(int k, int l, int r) {
    mx[k] = -INF;
    lz[k] = 0;
    rm[k] = lsh[r - 1];
    if (l == r) return;
    int mid = (l + r) / 2;
    build(k * 2, l, mid);
    build(k * 2 + 1, mid + 1, r);
}

void pushdown(int k) {
    if (lz[k]) {
        mx[k * 2] += lz[k];
        mx[k * 2 + 1] += lz[k];
        lz[k * 2] += lz[k];
        lz[k * 2 + 1] += lz[k];
        lz[k] = 0;
    }
}

long long query1(int k, int l, int r, int x, int y, long long cur = -INF) {
    if (x > r || y < l || mx[k] - 2LL * (y - rm[k]) * m <= cur) return -INF;
    if (l == r) return mx[k] - 1LL * (y - rm[k]) * m;
    pushdown(k);
    int mid = (l + r) / 2;
    cur = max(cur, query1(k * 2, l, mid, x, y, cur));
    cur = max(cur, query1(k * 2 + 1, mid + 1, r, x, y, cur));
    return cur;
}

long long query2(int k, int l, int r, int x) {
    if (l > x) return -INF;
    if (r <= x) return mx[k];
    pushdown(k);
    int mid = (l + r) / 2;
    return max(query2(k * 2, l, mid, x), query2(k * 2 + 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) / 2;
    if (x <= mid) modify(k * 2, l, mid, x, y);
    else modify(k * 2 + 1, mid + 1, r, x, y);
    mx[k] = max(mx[k * 2], mx[k * 2 + 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) / 2;
    add(k * 2, l, mid, x, y);
    add(k * 2 + 1, mid + 1, r, x, y);
    mx[k] = max(mx[k * 2], mx[k * 2 + 1]);
}

int getId(int x) {
    return lower_bound(lsh.begin(), lsh.end(), x) - lsh.begin() + 1;
}

int main() {
    freopen("soldier.in", "r", stdin);
    freopen("soldier.out", "w", stdout);
    
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%d %d", &n, &m);
        lsh.clear();
        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());
        
        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;
}