bool M1;
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define ull unsigned long long
#define LL __int128
#define db double
#define LD long double
#define Pii pair<int,int>
#define Pll pair<ll,ll>
#define Pull pair<ull,ull>
#define Pdb pair<db,db>
#define fir first
#define sec second
#define vec vector<int>
#define pb push_back
#define qlr cerr<<"qlr\n"
#define dyh cerr<<"dyh\n"
#define pc(x) __builtin_popcount(x)
#define uni(x,y) uniform_int_distribution<int>(x,y)(rng)
#define unl(x,y) uniform_int_distribution<ll>(x,y)(rng)
#define unr(x,y) uniform_real_distribution<double>(x,y)(rng)
#define F(i,a,b) for(int i=a,i##end=b;i<=i##end;i++)
#define UF(i,a,b) for(int i=a,i##end=b;i>=i##end;i--)
#define look_memory cerr<<'\n'<<abs(&M1-&M2)/1024.0/1024<<'\n'
#define look_time cerr<<'\n'<<clock()*1.0/CLOCKS_PER_SEC<<'\n'
mt19937 rng(time(0)^(*new int));
const ll INF=0x3f3f3f3f3f3f3f3f;
const int Mod=1e9+7;
template<typename T>
inline void inc(T &a,T b){
	if(b<0) b+=Mod;
	a+=b;
	if(a>=Mod) a-=Mod;
}
template<typename T>
inline void dec(T &a,T b){
	if(b<0) b+=Mod;
	a-=b;
	if(a<0) a+=Mod;
}
template<typename T>
inline void muc(T &a,T b){
	a=a*b%Mod;
}
template<typename T>
inline bool chkmin(T &a,T b){
	if(a<=b) return false;
	a=b;
	return true;
}
template<typename T>
inline bool chkmax(T &a,T b){
	if(a>=b) return false;
	a=b;
	return true;
}
const int M=6000;
ll T,n,m,K,ans;
ll a[1000010],b[1000010],sum[1000010];
ll f[6010][6010];
bool sit1(){
	F(i,1,n) if(a[i]!=b[i]) return 0;
	return 1;
}
void solve1(){
	ans=0;
	sum[n+1]=0;
	UF(i,n,1) sum[i]=sum[i+1]+a[i];
	F(i,1,n){
		if(m>=sum[i]);
		else if(m+a[i]/K<sum[i+1]){
			ll tmp=min(a[i]%K,m);
			ans+=a[i]-tmp,m=m-tmp+a[i]/K;
		}
		else{
			ll L=0,R=a[i],mid;
			while(L<=R){
				mid=(L+R)>>1;
				if(m+mid/K>=sum[i]-mid) R=mid-1;
				else L=mid+1;
			}
			chkmax(L,a[i]-m);
			ans+=L,m=sum[i+1];
		}
	}
	cout<<ans<<'\n';
}
void solve2(){
	F(i,0,n) F(j,0,M) f[i][j]=INF;
	f[0][m]=0;
	F(i,1,n){
		F(j,0,M){
			if(f[i-1][j]==INF) continue;
			F(k,0,min((ll)j,b[i])) chkmin(f[i][j-k+(a[i]-k)/K],f[i-1][j]+a[i]-k);
		}
	}
	ans=INF;
	F(i,0,M) chkmin(ans,f[n][i]);
	cout<<ans<<'\n';
}
void solve(){
	cin>>n>>m>>K;
	F(i,1,n) cin>>a[i];
	F(i,1,n) cin>>b[i];
	F(i,1,n) chkmin(b[i],a[i]);
	if(sit1()) solve1();
	else solve2();
}
bool M2;
int main(){
	// freopen("D.in","r",stdin);
	// freopen("D1.out","w",stdout);
	srand(time(0)^(*new int));
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>T;
	while(T--) solve();
	look_memory;
	look_time;
	return 0;
}
/*
g++ D1.cpp -o D1 -std=c++14 -O2&&./D1

6 3
1 1 4 5 1 4
1 1 4 -2
1 4 6 1
2 2 5 5

6 5
1 1 4 5 1 4
2 4 6 3
2 1 6 2
1 1 4 -2
1 4 6 1
2 2 5 5
*/