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

#define int long long

const int MAXN = 6005;
int memo[MAXN][MAXN];
int a[MAXN], b[MAXN];

int n, m, c;

int dp(int i, int j){
	if(memo[i][j] != -1) return memo[i][j];
	if(i >= n-1){
		return memo[i][j] = (a[i] - min(b[i], j));
	}
	memo[i][j] = LLONG_MAX;
	for(int k=0; k<= min(b[i], j); k++){
		memo[i][j] = min(memo[i][j], a[i] - k + dp(i+1, j - k + (a[i] - k)/c));
	}
	return memo[i][j];
}

void solve(){
	cin >> n >> m >> c;
	memset(memo, -1, sizeof(memo));
	for(int i=0; i<n; i++){
		cin >> a[i];
	}
	for(int i=0; i<n; i++){
		cin >> b[i];
	}
	cout << dp(0, m) << '\n';
}

signed main(){
	cin.tie(0); ios_base::sync_with_stdio(0);
	int T;
	cin >> T;
	while(T--){
		solve();
	}
	return 0;
}