#include <bits/stdc++.h>
#define dd(x) cout << #x << "\n"
#define d(x) cout << #x  << ": " << x << "\n"
using namespace std;
#define int long long
using pii = pair<int, int>;
using vpii = vector<pii>;
using vi = vector<int>;
using vii = vector<vector<int>>;
using a3 = array<int, 3>;
const int inf = 0x3f3f3f3f3f3f3f3fLL;

void solve() {
    int n, m; cin >> n >> m; 
    vector<int> a(n + 2), b(n + 1);
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    a[n + 1] = m;

    for(int i = 1; i <= n; i++) {
        cin >> b[i];
        b[i] += b[i - 1];
    }

    if(n == 1) {
        cout << min(0LL, b[1] - a[1]) << "\n";
        return ;
    }

    int p = (--lower_bound(b.begin(), b.end(), m)) - b.begin(), ans = 0;
    priority_queue<int> Q;
    for(int i = n + 1; i; i--) {
        int ed = p, st = p;
        while(st > 0 && a[i - 1] <= b[st] && b[st] < a[i]) --st;
        if(ed == st) {
            Q.push(a[i] - a[i - 1]);
            continue;
        }

        for(int j = st + 2; j <= ed; j++) {
            if(!Q.empty()) {
                ans += Q.top(); Q.pop();      
            }
        }

        
        if(ed != st) {
            ++st;
            if(Q.empty()) {
                ans += a[i] - b[st];
                Q.push(b[st] - a[i - 1]);
            } else if(a[i] - b[st] <= Q.top()) {
                ans += Q.top(); Q.pop();
            } else {
                ans += a[i] - b[st];
                int x = Q.top(); Q.pop();
                Q.push(x + b[st] - a[i - 1]);
            }
        }
        p = st - 1;
    }
    cout << ans << "\n";
}

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

/*
3
3 10
1 5 9
1 2 3
3 10
1 5 9
1 1 4
3 10
1 5 9
1 5 10

*/