#include<bits/stdc++.h>
#define MAXN 100000
#define rep(i,j,k) for (int i=(j);i<=(k);++i)
#define dep(i,j,k) for (int i=(j);i>=(k);--i)
using namespace std;
typedef long long LL;

priority_queue <int> grd;
int a[MAXN+5];
LL b[MAXN+5];

void solve() {
    int n,m;
    cin>>n>>m;
    rep(i,1,n) cin>>a[i];
    rep(i,1,n) cin>>b[i];
    sort(b+1,b+n+1);
    rep(i,1,n) b[i]+=b[i-1];
    a[n+1]=m;
    int l=1,r=1;
    LL ans=0;
    while (!grd.empty()) grd.pop();
    rep(i,1,n+1) {
        while (l<=n&&b[l]<a[i-1]) ++l;
        while (r<=n&&b[r]<a[i]) ++r;
        if (l<r) {
            if (!grd.empty()) {
                if (a[i]-a[i-1]+grd.top()>a[i]-b[l]) {
                    ans+=a[i]-a[i-1]+grd.top();
                    grd.pop();
                    grd.push(-a[i]+a[i-1]);
                    grd.push(0);
                } else {
                    ans+=a[i]-b[l];
                    if (a[i]-a[i-1]+grd.top()>0) {
                        int tmp=a[i]-a[i-1]+grd.top();
                        grd.push(-a[i]+b[l]+tmp);
                    } else grd.push(-a[i]+b[l]);
                }
            } else {
                ans+=a[i]-b[l];
                grd.push(-a[i]+b[l]);
            }
            rep(j,l+1,r-1) {
                grd.push(0);
            }
        } else {
            if (!grd.empty()) {
                if (a[i]-a[i-1]+grd.top()>0) {
                    ans+=a[i]-a[i-1]+grd.top();
                    grd.pop();
                    grd.push(-a[i]+a[i-1]);
                }
            }
        }
    }
    cout<<ans<<"\n";
    return;
}

int main() {
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int t;
    cin>>t;
    while (t--) solve();
    return 0;
}