// #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];

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]
    per (i, n, 1) {
        ll t = min(b[i], a[i] % c);
        rep (j, i - 1, n) cmin(t, s[j]);
        x[i] += t;
        rep (j, i - 1, n) s[j] -= t;
    }
    per (i, n, 1) {
        ll t = min((b[i] - x[i]) / c, s[i - 1] / c);
        rep (j, i, n) cmin(t, s[j] / (c + 1));
        x[i] += t * c;
        s[i - 1] -= t * c;
        rep (j, i, n) s[j] -= t * (c + 1);
    }

    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 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;}