#include<bits/stdc++.h>

#define ll long long
#define pi pair<ll,ll>
#define vi vector<ll>
#define cpy(x,y,s) memcpy(x,y,sizeof(x[0])*(s))
#define mset(x,v,s) memset(x,v,sizeof(x[0])*(s))
#define all(x) begin(x),end(x)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define ary array
#define IL inline

#define mod 998244353
#define N 300005

using namespace std;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0' || ch>'9')f=(ch=='-'?-1:f),ch=getchar();
    while(ch>='0' && ch<='9')x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
    return x*f;
}
void write(ll x){
    if(x<0)x=-x,putchar('-');
    if(x/10)write(x/10);
    putchar(x%10+'0');
}

ll a[N],b[N];
priority_queue<ll,vector<ll>,greater<ll> > q;

void solve(){
    while(q.size())q.pop();
    ll n=read(),m=read();
    for(ll i=1;i<=n;i++)a[i]=read();
    for(ll i=1;i<=n;i++)b[i]=read();
    sort(b+1,b+n+1);
    for(ll i=1;i<=n;i++)b[i]+=b[i-1];
    ll pos=n+1,res=0;
    while(pos-1!=0 && b[pos-1]>m)pos--;
    a[n+1]=m;
    for(ll i=n;i>=0;i--){
        vi S;
        while(pos-1!=0 && b[pos-1]>=a[i])pos--,S.pb(b[pos]);
        if(!S.size()){
            q.push(a[i+1]-a[i]);continue;
        }
        reverse(S.begin(),S.end());
        for(ll i=S.size()-1;i>=1;i--){
            ll v=S[i];
            if(q.size())res+=q.top(),q.pop();
        }
        //cerr<<i<<' '<<q.size()<<' '<<res<<' '<<a[i+1]<<' '<<S[0]<<endl;
        if(q.size() && q.top()>a[i+1]-S[0]){
            res+=q.top();q.pop();q.push(a[i+1]-a[i]);
        }
        else{
            ll opt=S[0]-a[i];
            if(q.size())opt+=q.top(),q.pop();
            res+=a[i+1]-S[0];q.push(opt);
        }
    }
    //cerr<<endl;
    write(res);putchar('\n');
}

int main(){
    #ifdef EAST_CLOUD
    freopen("a.in","r",stdin);
    freopen("a.out","w",stdout);
    #endif
    
    ll T=read();while(T--)solve();
    return 0;
}
//cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
//cerr<<"\n"<<clock()*1.0/CLOCKS_PER_SEC*1000<<"ms\n";