#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define pii pair<int, int>
void solve();

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int T = 1;
    cin >> T;
    while (T--)solve();
    return 0;
}
//const int mod = 998244353;


void solve() {
    int n;
    int m;
    cin>>n>>m;
    vector<int>a(n+1),b(n+2);
    for(int i=1;i<=n;i++)cin>>a[i];
    for(int i=1;i<=n;i++)cin>>b[i];
    b[n+1]=1e18;
    sort(b.begin()+1,b.end());
    a.push_back(b[1]);
    sort(a.begin()+1,a.end());
    for(int i=1;i<=n;i++){
        b[i]+=b[i-1];
//        cout<<"b== ";cout<<b[i]<<endl;;
    }

    priority_queue<int,vector<int>,greater<int>>q1,q2;
    for(int i=1;i<=n;i++){
        if(b[i]>m)break;
        auto it= lower_bound(a.begin()+1,a.end(),b[i]);
        while(it!=a.end()&&(*it)<min(m+1,b[i+1])){
            int x=*it;
            int y=m;
            it++;
            if(it!=a.end())y=*it;
//            cout<<"i== "<<i<<' ';
//            cout<<"===="<<x<<endl;
            if(1)q2.push(y-x);
            else q1.push(y-x);
        }
        auto t= lower_bound(a.begin()+1,a.end(),b[i]+1);
        int x=b[i];
        while(t!=a.end()&&(*t)<=min(m+1,b[i+1])){
            int y=m;
            y=*t;
            if(1)q1.push(y-x);
            x=y;
            t++;
        }
        while(q2.size()>i){
            q2.pop();
        }
        while(q1.size()>i){
            q1.pop();
        }
    }
    int ans=0;
    int sum=0;
    while(q1.size()){
        sum+=q1.top();
        q1.pop();
        ans=sum;
    }
    sum=0;
    while(q2.size()){
//        cout<<"---"<<q2.top()<<endl;
        sum+=q2.top();
        q2.pop();
        ans=max(ans,sum);
    }
    cout<<ans<<endl;
}
/*
2
3 13
6 7 13
1 9 999
4 14
6 7 13 14
1 9 999 999
 */