#include<bits/stdc++.h>
#define fore(i,l,r)	for(int i=(int)(l);i<(int)(r);++i)
#define fi first
#define se second
#define endl '\n'
#define ull unsigned long long
#define ALL(v) v.begin(), v.end()
#define Debug(x, ed) std::cerr << #x << " = " << x << ed;

const int INF=0x3f3f3f3f;
const long long INFLL=1e18;

typedef long long ll;

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    int t;
    std::cin >> t;
    while(t--){
    	int n, m;
    	std::cin >> n >> m;
    	std::vector<int> a(n + 2);
    	fore(i, 1, n + 1) std::cin >> a[i];
    	a[n + 1] = m;
    	std::vector<int> b(n);
    	fore(i, 0, n) std::cin >> b[i];
    	std::sort(ALL(b));
    	std::vector<int> t;
    	int lst = 0;
    	for(auto x : b){
    		if(lst + x >= m) break;
    		lst += x;
    		t.push_back(lst);
    	}
    	
    	int idx = t.size() - 1;
    	int ans = 0;
    	std::priority_queue<int> q;
    	for(int i = n + 1; i > 0; --i){
    		int l = a[i - 1], r = a[i];
    		int cnt = 0, t1 = 0;
    		while(idx >= 0 && t[idx] >= r) --idx;
    		while(idx >= 0 && t[idx] >= l){
    			++cnt;
    			t1 = t[idx];
    			--idx;
    		}
    		if(!cnt) q.push(r - l);
    		else{
    			fore(k, 0, cnt - 1){
    				if(q.empty()) break;
    				ans += q.top();
    				q.pop();
    			}
    			ans += r - t1;
    			if(q.empty() || q.top() < r - t1){
    				int x = (q.empty() ? 0 : q.top());
    				q.push(t1 - l + x);
    			}
    			else{
    				ans += q.top();
    				q.pop();
    				q.push(r - l);
    			}
    		}
    	}
    	
    	std::cout << ans << endl;
    }
    
    return 0;
}