//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
//#pragma GCC optimize("Ofast,fast-math")
//#pragma GCC target("avx,avx2")
//#pragma GCC optimize(2)
//#pragma GCC optimize(3)
//#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef double db;
#define F(i, a, b) for(int i = a; i <= (b); ++i)
#define F2(i, a, b) for(int i = a; i < (b); ++i)
#define dF(i, a, b) for(int i = a; i >= (b); --i)
template<typename T> void debug(string s, T x) {
	cerr << "[" << s << "] = [" << x << "]\n";
}
template<typename T, typename... Args> void debug(string s, T x, Args... args) {
	for (int i = 0, b = 0; i < (int)s.size(); i++) if (s[i] == '(' || s[i] == '{') b++;
		else if (s[i] == ')' || s[i] == '}') b--;
		else if (s[i] == ',' && b == 0) {
			cerr << "[" << s.substr(0, i) << "] = [" << x << "] | ";
			debug(s.substr(s.find_first_not_of(' ', i + 1)), args...);
			break;
		}
}
#ifdef ONLINE_JUDGE
	#define Debug(...)
#else
	#define Debug(...) debug(#__VA_ARGS__, __VA_ARGS__)
#endif
#define pb push_back
#define fi first
#define se second
#define Mry fprintf(stderr, "%.3lf MB\n", (&Med - &Mbe) / 1048576.0)
#define Try cerr << 1e3 * clock() / CLOCKS_PER_SEC << " ms\n";
typedef long long ll;
// namespace Fread {const int SIZE = 1 << 17; char buf[SIZE], *S, *T; inline char getchar() {if (S == T) {T = (S = buf) + fread(buf, 1, SIZE, stdin); if (S == T) return '\n';} return *S++;}}
// namespace Fwrite {const int SIZE = 1 << 17; char buf[SIZE], *S = buf, *T = buf + SIZE; inline void flush() {fwrite(buf, 1, S - buf, stdout), S = buf;} inline void putchar(char c) {*S++ = c;if (S == T) flush();} struct NTR {~NTR() {flush();}} ztr;}
// #ifdef ONLINE_JUDGE
// #define getchar Fread::getchar
// #define putchar Fwrite::putchar
// #endif
inline int ri() {
	int x = 0;
	bool t = 0;
	char c = getchar();
	while (c < '0' || c > '9') t |= c == '-', c = getchar();
	while (c >= '0' && c <= '9') x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
	return t ? -x : x;
}
inline void wi(int x) {
	if (x < 0) {
		putchar('-'), x = -x;
	}
	if (x > 9) wi(x / 10);
	putchar(x % 10 + 48);
}
inline void wi(int x, char s) {
	wi(x), putchar(s);
}
bool Mbe;
// mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int mod = 998244353;
const int inf = 0x3f3f3f3f;
const ll infll = 0x3f3f3f3f3f3f3f3f;
const int _ = 2e5 + 5;

int n, m, a[_], b[_];

bool vis[_];

map<pii, int> mp;

//int val[_];

struct sgt {
	struct node {
		int s, tg, lc, rc;
	} tr[_ * 30];
	int cnt;
	int rt;
	void init() {
		F(i, 0, cnt + 1) tr[i].s = tr[i].tg = tr[i].lc = tr[i].rc = 0;
		cnt = 0;
		rt = 0;
	}
	void upd(int &o, int l, int r, int L, int R, int v) {
		if (L > R) return;
		if (!o) o = ++cnt;
		if (L <= l && r <= R) {
			tr[o].s += v;
			tr[o].tg += v;
			return;
		}
		int mid = (l + r) >> 1;
		if (L <= mid) upd(tr[o].lc, l, mid, L, R, v);
		if (R > mid) upd(tr[o].rc, mid + 1, r, L, R, v);
		tr[o].s = max(tr[tr[o].lc].s, tr[tr[o].rc].s);
	}
	int qry(int o, int l, int r, int p, int tg = 0) {
		if (l == r) {
			return tr[o].s + tg;
		}
		int mid = (l + r) >> 1;
		return p <= mid ? qry(tr[o].lc, l, mid, p, tg + tr[o].tg) : qry(tr[o].rc, mid + 1, r, p, tg + tr[o].tg);
	}
} tr;

int s[_], val[_], cnt[_];

void solve() {
	n = ri(), m = ri();
	F(i, 1, n) a[i] = ri();
//	int n2 = n;
//	tr.init();
	F(i, 1, n) b[i] = ri();
	sort(b + 1, b + n + 1);
	F(i, 1, n) s[i] = s[i - 1] + b[i];
	a[n + 1] = m;
	F(i, 1, n + 1) val[i] = cnt[i] = 0;
	int j = 0;
	F(i, 1, n) {
		while(j <= n + 1 && a[j] < s[i]) j++;
		if(j <= n + 1) val[j] = max(val[j], a[j] - s[i]), cnt[j]++;
	}
	int ans = 0;
	priority_queue<int> q;
	F(i, 1, n + 1) {
		if(cnt[i]) {
			int W = ans + val[i];
			int w1 = val[i], w2 = (!q.empty()) ? a[i] - a[i - 1] + q.top() : 0;
			if(w1 >= w2) {
				ans += w1;
				q.push(-w1);
				q.push(-(w1 - w2));
			} else {
				ans += w2;
				if(!q.empty()) {
					q.pop();
					q.push(-w2);
				}
				q.push(0);
			}
//			if(!q.empty() && a[i] - a[i - 1] + q.top() > 0) {
//				ans += a[i] - a[i - 1] + q.top();
//				q.pop();
//				q.push(-(a[i] - a[i - 1]));
//			}
//			if(ans < W) {
//				q.push(-(W - ans));
//				ans = W;
//			} else q.push(0);
			F(j, 1, cnt[i] - 1) q.push(0);
		} else {
			if(!q.empty() && a[i] - a[i - 1] + q.top() > 0) {
				ans += a[i] - a[i - 1] + q.top();
				q.pop();
				q.push(-(a[i] - a[i - 1]));
			}
		}
	}
	cout << ans << '\n';
}

bool Med;
signed main() {
	// Mry;
	int T = ri();
	while (T--) {
		solve();
	}
	// Try;
	return 0;
}

/*
1
9 879847766
125098132 150509852 181700303 196375322 519766842 560891576 609151480 721527163 805167083
99031467 66330518 6283986 21388462 41109537 83628243 116141243 144052767 192448599

10000
9 879847766
125098132 150509852 181700303 196375322 519766842 560891576 609151480 721527163 805167083
99031467 66330518 6283986 21388462 41109537 83628243 116141243 144052767 192448599
8 30
5 12 16 19 20 23 25 27
3 1 1 4 2 8 2 3
8 30
4 10 13 16 17 20 23 27
6 3 1 2 3 4 7 2
*/