1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define ll long long
 4 #define ull unsigned long long
 5 #define mst(a,b) memset((a),(b),sizeof(a))
 6 #define mp(a,b) make_pair(a,b)
 7 #define pi acos(-1)
 8 #define pii pair<int,int>
 9 #define pb push_back
10 const int INF = 0x3f3f3f3f;
11 const double eps = 1e-6;
12 const int MAXN = 1e5 + 10;
13 const int MAXM = 1e3 + 10;
14 const ll mod = 100000073;
15
16 int n;
17 ll p,ans;
18 vector<pair<int,ll> >vec[MAXN];
19 ll dist[MAXN],dp[MAXN];
20 int q[MAXN];
21
22 ll sqr(ll x) {
23     return x * x;
24 }
25
26 ll getup(int j,int k) {
27     return dp[j] + sqr(dist[j]) - (dp[k] + sqr(dist[k]));
28 }
29
30 ll getdown(int j,int k) {
31     return 2ll * (dist[j] - dist[k]);
32 }
33
34 void dfs(int u,int fa,int st,int en) {
35     dp[u] = dist[u] * dist[u];
36     int head = st, tail = en;
37     while(head + 1 < tail && getup(q[head + 1],q[head]) <= dist[u] * getdown(q[head + 1],q[head])) head++;
38     dp[u] = min(dp[u], dp[q[head]] + sqr(dist[u] - dist[q[head]]) + p);
39     while(head + 1 < tail && getup(u,q[tail - 1]) * getdown(q[tail - 1],q[tail - 2]) <= getup(q[tail - 1],q[tail - 2]) * getdown(u,q[tail - 1]))
40         tail--;
41     q[tail++] = u;
42     int pre = u;
43     ans = max(ans, dp[u]);
44     for(int i = 0; i < vec[u].size(); i++) {
45         int v = vec[u][i].first;
46         ll w = vec[u][i].second;
47         if(v == fa) continue;
48         dist[v] = dist[u] + w;
49         dfs(v,u,head,tail);
50     }
51     q[tail - 1] = pre;
52 }
53
54 int main() {
55 #ifdef local
56     freopen("data.txt", "r", stdin);
57 #endif
58     int t;
59     scanf("%d",&t);
60     while(t--) {
61         scanf("%d%lld",&n,&p);
62         for(int i = 1; i <= n; i++) {
63             vec[i].clear();
64         }
65         for(int i = 1; i < n; i++) {
66             int u,v;
67             ll w;
68             scanf("%d%lld%lld",&u,&v,&w);
69             vec[u].push_back(make_pair(v,w));
70             vec[v].push_back(make_pair(u,w));
71         }
72         dist[1] = 0;
73         int head = 0, tail = 0;
74         q[tail++] = 1;
75         ans = 0;
76         dfs(1,0,0,1);
77         printf("%lld\n",ans);
78     }
79     return 0;
80 }