#include <bits/stdc++.h>
using i64 = long long;
const int N = 1e5;
int n, m, a[N + 5];
i64 b[N + 5], ans;
std::priority_queue<i64> hp;
void solve() {
    std::cin >> n >> m;
    for (int i = 1; i <= n; ++i) std::cin >> a[i];
    a[n + 1] = m;
    for (int i = 1; i <= n; ++i) std::cin >> b[i];
    std::sort(b + 1, b + 1 + n);
    for (int i = 1; i <= n; ++i) b[i] += b[i - 1];
    int p = n;
    while (b[p] >= m) --p;
    for (int i = n; ~i; --i) {
        int q = p;
        while (p and b[p] >= a[i]) {
            i64 val = hp.size() ? hp.top() : 0;
            if (hp.size()) hp.pop();
            if (p - 1 and b[p - 1] >= a[i]) ans += val;
            else {
                if (val > a[i + 1] - b[p]) hp.push(a[i + 1] - a[i]), ans += val;
                else hp.push(val + b[p] - a[i]), ans += a[i + 1] - b[p];
            }
            --p;
        }
        if (p == q) hp.push(a[i + 1] - a[i]);
    }
    std::cout << ans << "\n";
    while (hp.size()) hp.pop();
    ans = 0;
}
int main() {
    std::ios::sync_with_stdio(false), std::cin.tie(0), std::cout.tie(0);
    int _;
    for (std::cin >> _; _--;) solve();
    return 0;
}