#include<bits/stdc++.h>
#define endl "\n"
using namespace std;
using ll = long long;
const int maxn = 1e5 + 10;
ll a[maxn],b[maxn];
void solve(void)
{
	ll n,m;
	cin>>n>>m;
	vector<pair<ll,ll>> vec;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		vec.emplace_back(a[i],2);
	}
	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];
		if(b[i]<=m)
		{
			vec.emplace_back(b[i],1);
		}
	}
	vec.emplace_back(m,2);
	sort(vec.begin(),vec.end(),greater<pair<ll,ll>>());
	priority_queue<ll,vector<ll>,less<ll>> pq;
	ll last=-1,ans=0,vis=0;
	for(auto [pos,c] : vec)
	{
		//cerr<<"###"<<pos<<" "<<c<<endl;
		if(c==2)
		{
			if(~last)
			{
				if(vis&&!pq.empty())
				{
					ll mx=pq.top();
					pq.pop();
					pq.emplace(mx+last-pos);
				}
				else
				{
					pq.emplace(last-pos);
				}
			}
			last=pos;
			vis=0;
		}
		else
		{
			if(!pq.empty())
			{
				if(last-pos>pq.top())
				{
					ans+=last-pos;
					last=pos;
					vis=1;
				}
				else
				{
					ans+=pq.top();
					pq.pop();
				}
			}
			else
			{
				ans+=last-pos;
				last=pos;
				vis=1;
			}
		}
	}
	cout<<ans<<endl;
}
int main(void)
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin>>t;
	while(t--)
	{
		solve();
	}
	return 0;
}