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

const int N=1e5+10;
int a[N],b[N],n,m,del[N];
struct tmp{
	int t,op,id;
	bool operator < (const tmp x) const {
		if (t==x.t) return op<x.op;
		return t<x.t;
	}
}s[N<<2];

void solve() {
	cin>>n>>m;
	for (int i=1;i<=n;i++) cin>>a[i]; a[n+1]=m;
	for (int i=1;i<=n;i++) cin>>b[i];
	sort(b+1,b+n+1);
	for (int i=1;i<=n;i++) b[i]=b[i-1]+b[i];
	int p=0;
	for (int i=1;i<=n;i++) s[++p]={a[i],0,i},del[i]=0;
	for (int i=1;i<=n;i++) if (b[i]<=m) s[++p]={b[i],1,i}; else b[i]=m; b[n+1]=m;
	sort(s+1,s+p+1); s[p+1]={m,0,0};
	
	int bef=0,nxt=1,cnt=0,fl=1,ans=0;
	priority_queue<int,vector<int>,greater<int>> q;
	for (int i=1;i<=p;i++) {
		int t=s[i].t,op=s[i].op,id=s[i].id;
	//	cout<<t<<' '<<op<<' '<<id<<'\n'<<flush;
		if (op==0) {
			bef=id,nxt=id+1; fl=1;
			if (cnt>=1) {
				--cnt; fl=0;
				q.push(a[nxt]-a[bef]);
				ans+=a[nxt]-a[bef];
			} else if (!q.empty()) {
				int T=s[i+1].t,OP=s[i+1].op,ID=s[i+1].id,dur;
				dur=T-t;
				if (q.top()<=dur) {
					ans=ans-q.top()+a[nxt]-a[bef];
					q.pop(); q.push(a[nxt]-a[bef]);
					fl=0;
				} else {
					if (OP==1) {
						int las=q.top(); 
						if (a[nxt]-a[bef]<=las) continue;
						q.pop(); int xxx=a[nxt]-T-(a[nxt]-a[bef]-las);
						q.push(xxx); q.push(a[nxt]-a[bef]); del[ID]=1; fl=0;
						// las -> 
						// q.push(min(a[nxt]-a[bef],las-dur));
						// q.push(min(xxx-dur,)); q.push(a[nxt]-T); del[ID]=1; fl=0;
					}
				}
			}
		}
		else {
			if (del[id]) continue;
			if (fl) {
				q.push(a[nxt]-t); fl=0;
				ans+=a[nxt]-t; 
			} else ++cnt;
		} // cout<<1<<flush<<'\n';
	//	cout<<ans<<'\n';
	}
	cout<<ans<<'\n';
}

signed main() {
	ios::sync_with_stdio(0);
	int T; cin>>T; while (T--) solve();
}