// #pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#define rep(i,l,r) for (int i(l), i##end(r); i <= i##end; ++i)
#define per(i,r,l) for (int i(r), i##end(l); i >= i##end; --i)
#define ll long long
#define fi first
#define se second
#define eb emplace_back
#define File(filename) freopen(filename".in", "r", stdin), freopen(filename".out", "w", stdout)
#define clr(arr) memset(arr, 0, sizeof(arr))
using namespace std;
template <typename Tx> inline void read(Tx &x) {x = 0; bool f = 0; char ch = getchar(); while (ch < '0' || ch > '9') f ^= ch == '-', ch = getchar(); while (ch <= '9' && ch >= '0') x = x * 10 + ch - '0', ch = getchar(); if (f) x = -x;}
template <typename Tx, typename ...Ty> inline void read(Tx &x, Ty &...y) {read(x); read(y...);}
template <typename Tx> inline void O_write(Tx x) {if (x > 9) O_write(x / 10); putchar('0' + x % 10);}
template <typename Tx> inline void write(Tx x, char ch = '\n') {O_write(x < 0 ? (putchar('-'), -x) : x); putchar(ch);}
template <typename T> inline void cmax(T &x, T y) {if (x < y) x = y;}
template <typename T> inline void cmin(T &x, T y) {if (x > y) x = y;}
namespace Main {

const int N = 1e6 + 9;

int n, m, c;
ll a[N], b[N], x[N], s[N], d[N];

const ll inf = 0x3f3f3f3f3f3f3f3f;

struct SegmentTree {
    #define lc (p << 1)
    #define rc (p << 1 | 1)
    ll tag[N * 4], mn[N * 4];
    #define pushup(p) mn[p] = min(mn[lc], mn[rc])
    void add_tag(int p, ll v) {
        tag[p] += v, mn[p] += v;
    }
    void pushdown(int p) {
        if (tag[p]) {
            add_tag(lc, tag[p]);
            add_tag(rc, tag[p]);
            tag[p] = 0;
        }
    }
    void build(int p = 1, int l = 0, int r = n) {
        tag[p] = 0;
        if (l == r) {
            mn[p] = s[l];
            return ;
        }
        int mid = (l + r) >> 1;
        build(lc, l, mid), build(rc, mid + 1, r);
        pushup(p);
    }
    void modify(int ql, int qr, ll v, int p = 1, int l = 0, int r = n) {
        if (qr < l || r < ql) return;
        if (ql <= l && r <= qr) return add_tag(p, v);
        pushdown(p);
        int mid = (l + r) >> 1;
        modify(ql, qr, v, lc, l, mid), modify(ql, qr, v, rc, mid + 1, r);
        pushup(p);
    }
    ll querymin(int ql, int qr, int p = 1, int l = 0, int r = n) {
        if (ql <= l && r <= qr) return mn[p];
        pushdown(p);
        int mid = (l + r) >> 1;
        if (qr <= mid) return querymin(ql, qr, lc, l, mid);
        if (mid < ql) return querymin(ql, qr, rc, mid + 1, r);
        return min(querymin(ql, qr, lc, l, mid), querymin(ql, qr, rc, mid + 1, r));
    }
} sgt;

    // rep (_, 1, n) {
        // ll p = 0;
        // ll z = -1;
        // rep (i, 1, n) {
        //     ll t = min(b[i] - x[i], s[i - 1]);
        //     rep (j, i, n) cmin(t, s[j] - 1);
        //     if (t >= z) p = i, z = t;
        // }
        // if (z <= 0) break;
        // x[p] += z;
        // s[p - 1] -= z;
        // rep (i, p, n) s[i] -= (z + 1);
    // }

ll qry(int i) {
    ll t = min(sgt.querymin(i - 1, i - 1), sgt.querymin(i, n) - 1);
    return t;
}
void put(int p, ll z) {
    if (z <= 0) return ;
    x[p] += z;
    sgt.modify(p - 1, p - 1, -z);
    sgt.modify(p, n, -(z + 1));
}

priority_queue <int> pq;

inline void skymaths() {
    read(n, m, c);

    rep (i, 1, n) read(a[i]);
    rep (i, 1, n) read(b[i]);
    s[0] = m;
    rep (i, 1, n) {
        s[i] = s[i - 1] + a[i] / c;
    }
    // s'[i] = s[i] - x[i + 1]
    {
        ll mn = inf; rep (i, 0, n) d[i] = 0;
        per (i, n, 1) {
            ll t = min(b[i], a[i] % c);
            cmin(mn, s[i - 1]); cmin(t, mn);
            // rep (j, i - 1, n) cmin(t, s[j]);
            x[i] += t;
            d[i - 1] -= t;
            mn -= t;
            // rep (j, i - 1, n) s[j] -= t;
        }
        rep (i, 1, n) d[i] += d[i - 1];
        rep (i, 0, n) s[i] += d[i];
    }
    {
        ll mn = inf; rep (i, 0, n) d[i] = 0;
        per (i, n, 1) {
            ll t = min((b[i] - x[i]) / c, s[i - 1] / c);
            cmin(mn, s[i]); cmin(t, mn / (c + 1));
            // rep (j, i, n) cmin(t, s[j] / (c + 1));
            x[i] += t * c;
            s[i - 1] -= t * c;
            mn -= t * (c + 1);
            d[i] -= t * (c + 1);
            // rep (j, i, n) s[j] -= t * (c + 1);
        }
        rep (i, 1, n) d[i] += d[i - 1];
        rep (i, 0, n) s[i] += d[i];
    }

    // rep (_, 1, n) {
    //     ll p = 0;
    //     ll z = -1;
    //     rep (i, 1, n) {
    //         ll t = min(b[i] - x[i], s[i - 1]);
    //         rep (j, i, n) cmin(t, s[j] - 1);
    //         if (t >= z) p = i, z = t;
    //     }
    //     if (z <= 0) break;
    //     x[p] += z;
    //     s[p - 1] -= z;
    //     rep (i, p, n) s[i] -= (z + 1);
    // }

    sgt.build();
    static pair <ll, int> pr[N];
    static ll nw[N];
    rep (i, 1, n) pr[i] = make_pair(b[i] - x[i], i);
    sort(pr + 1, pr + n + 1, greater<pair <ll, int> >());
    rep (i, 1, n) nw[i] = pr[i].first;
    int cnt = unique(nw + 1, nw + n + 1) - nw - 1, r = 1;
    nw[cnt + 1] = -1;
    while (!pq.empty()) pq.pop();
    rep (_, 1, cnt + 1) {
        ll w = nw[_];
        while (!pq.empty()) {
            // no limit
            int i = pq.top();
            ll z = qry(i);
            // qry only care s limit not b[i] - x[i]!!!
            if (z >= w) {
                put(i, z);
                pq.pop();
            } else break;
        }
        while (r <= n && pr[r].fi >= w) pq.push(pr[r++].se);
        while (!pq.empty()) {
            int i = pq.top();
            ll z = qry(i);
            // qry only care s limit not b[i] - x[i]!!!
            if (z >= w) {
                put(i, z);
                pq.pop();
            } else break;
        }
    }

    ll ans(0);
    rep (i, 1, n) ans += a[i] - x[i];
    
    rep (i, 1, n) x[i] = 0;

    write(ans);
}

signed main() {
    //freopen("a.in", "r", stdin);
    int T = 1;
    read(T);
    rep (Tid, 1, T) {
        skymaths();
    }
    return 0;
} } signed main() { Main::main(); return 0;}