#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;

int a[N], b[N], dlt[N];
long long s[N], ts[N];

signed main() {
    int T; scanf("%d", &T);
    while (T--) {
        int n, m, c; scanf("%d%d%d", &n, &m, &c);
        s[0] = m;
        for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
        for (int i = 1; i <= n; ++i) scanf("%d", &b[i]);
        for (int i = 1; i <= n; ++i) {
            b[i] = min(b[i], a[i]);
            s[i] = s[i - 1] + a[i] / c;
        }
        for (int i = n; i >= 1; --i) {
            s[i] = s[i - 1];
        }
        for (int i = 1; i <= n; ++i) ts[i] = 0;
        long long mn = s[n];
        for (int i = n; i >= 1; --i) {
            long long t = min(a[i] % c, b[i]);
            mn = min(mn, s[i]), t = min(t, mn);
            a[i] -= t, b[i] -= t, mn -= t, ts[i] += t;
        }
        for (int i = 1; i <= n; ++i) {
            ts[i] += ts[i - 1], s[i] -= ts[i];
        }
        for (int i = 1; i <= n; ++i) ts[i] = 0;
        mn = 1e18;
        for (int i = n; i >= 1; --i) {
            if (a[i] % c != 0) continue;
            long long t = min((long long)b[i], s[i]) / c;
            if (i != n) mn = min(mn, s[i + 1]);
            t = min(t, mn / (c + 1));
            a[i] -= t * c, b[i] -= t * c, s[i] -= t * c, mn -= t * (c + 1), ts[i + 1] += t * (c + 1);
        }
        for (int i = 1; i <= n; ++i) {
            ts[i] += ts[i - 1], s[i] -= ts[i];
        }
        while (1) {
            for (int i = 1; i <= n; ++i) {
                dlt[i] = 0;
                if (a[i] % c != 0) continue;
                long long o = min((long long)min(b[i], c - 1), s[i]);
                for (int j = i + 1; j <= n; ++j) o = min(o, s[j] - 1);
                dlt[i] = o;
            }
            int p = max_element(dlt + 1, dlt + n + 1) - dlt;
            if (dlt[p] <= 0) break;
            a[p] -= dlt[p], b[p] -= dlt[p], s[p] -= dlt[p];
            for (int i = p + 1; i <= n; ++i) s[i] -= dlt[p] + 1;
        }
        printf("%lld\n", accumulate(a + 1, a + n + 1, 0ll));
    }
    return 0;
}