#include <bits/stdc++.h>
#define FOR(i, l, r) for (int i = (l); i <= (r); ++i)
#define ROF(i, r, l) for (int i = (r); i >= (l); --i)
#define popc(x) __builtin_popcount(x)
#define allc(x) (x).begin(), (x).end()
#define SZ(v) (int)v.size()
#define PII pair<int, int>
#define PB push_back
#define MP make_pair
#define FI first
#define SE second
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
bool Mbe;
template <typename A, typename B>
void chkmax(A &a, B b) {
    a = a > b ? a : b;
}
template <typename A, typename B>
void chkmin(A &a, B b) {
    a = a < b ? a : b;
}
namespace lyl {
    const int N = 5e5 + 5;
    const ll inf = 1e18;
    struct sgt {
        ll tr[N << 2], tag[N << 2];
        void init() {
            FOR (i, 1, (N << 2) - 1) {
                tr[i] = -inf; 
            }
            memset(tag, 0, sizeof(tag));
        }
        void upd(int v, int k) {
            tag[v] += k;
            tr[v] += k;
        }
        void pushdown(int v) {
            upd(v << 1, tag[v]);
            upd(v << 1 | 1, tag[v]);
            tag[v] = 0;
        }
        void modify(int v, int l, int r, int L, int R, ll k) {
            if (L <= l && r <= R) {
                upd(v, k);
                return;
            }
            pushdown(v);
            int mid = l + r >> 1;
            if (L <= mid) {
                modify(v << 1, l, mid, L, R, k);
            }
            if (R > mid) {
                modify(v << 1 | 1, mid + 1, r, L, R, k);
            }
            tr[v] = max(tr[v << 1], tr[v << 1 | 1]);
        }
        void update(int v, int l, int r, int p, ll k) {
            if (l == r) {
                tr[v] = k;
                tag[v] = 0;
                return;
            }
            pushdown(v);
            int mid = l + r >> 1;
            if (p <= mid) {
                update(v << 1, l, mid, p, k);
            }
            if (p > mid) {
                update(v << 1 | 1, mid + 1, r, p, k);
            }
            tr[v] = max(tr[v << 1], tr[v << 1 | 1]);
        } 
        ll query(int v, int l, int r, int L, int R) {
            if (L > r || R < l) {
                return -inf;
            }
            if (L <= l && r <= R) {
                return tr[v];
            }
            pushdown(v);
            int mid = l + r >> 1;
            return max(query(v << 1, l, mid, L, R), query(v << 1 | 1, mid + 1, r, L, R));
        }
    } tpre, tsuf;
    int n, a[N];
    ll m, tmp[N], f[N], b[N]; 
    void solve() {
        cin >> n >> m;
        FOR (i, 1, n) {
            cin >> a[i] >> b[i];
            if (b[i] < 0) {
                tmp[i] = a[i] - 1;
            } else {
                tmp[i] = a[i];
            }
        }
        tmp[n + 1] = 0;
        sort(tmp + 1, tmp + n + 2);
        int k = unique(tmp + 1, tmp + n + 2) - tmp - 1;
        FOR (i, 1, n) {
            a[i] = lower_bound(tmp + 1, tmp + k + 1, a[i]) - tmp;
        }
        f[1] = 0;
        FOR (i, 2, k) {
            f[i] = -inf;
        }
        tpre.init();
        tsuf.init();
        tpre.update(1, 1, k, 1, 0);
        tsuf.update(1, 1, k, 1, 0);
        FOR (i, 1, n) {
            if (b[i] < 0) {
                --a[i];
                f[a[i]] = tsuf.query(1, 1, k, a[i], a[i]);
                chkmax(f[a[i]], tsuf.query(1, 1, k, a[i] + 1, n));
            } else {
                f[a[i]] = tsuf.query(1, 1, k, a[i], a[i]);
                chkmax(f[a[i]], tpre.query(1, 1, k, 1, a[i] - 1) - tmp[a[i]] * m);
            }
            tpre.update(1, 1, k, a[i], f[a[i]] + tmp[a[i]] * m);
            tsuf.update(1, 1, k, a[i], f[a[i]]);
            if (b[i] < 0 && a[i] < k) {
                tpre.modify(1, 1, k, a[i] + 1, k, b[i]);
                tsuf.modify(1, 1, k, a[i] + 1, k, b[i]);
            }
            if (b[i] > 0) {
                tsuf.modify(1, 1, k, a[i], k, b[i]);
                tpre.modify(1, 1, k, a[i], k, b[i]);
            }
        }
        cout << tsuf.tr[1] << '\n';
    }
}
bool Meb;
int main() {
    // freopen(".in", "r", stdin);
    // freopen(".out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int T;
    cin >> T;
    while (T--) {
        lyl::solve();
    }
    // cerr << "Space: " << abs(&Meb - &Mbe) / 1024.0 / 1024.0 << "MB\n";
    // cerr << "Time: " << clock() * 1000.0 / CLOCKS_PER_SEC << "ms\n";
    return 0;
}