#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>using namespace std;#define N 100001typedef long long LL;int P;int front[N],to[N<<1],nxt[N<<1],val[N<<1],tot;int dis[N];int head,tail,q[N];
LL dp[N];void read(int &x)
{x=0; char c=getchar();while(!isdigit(c)) c=getchar();while(isdigit(c)) { x=x*10+c-'0'; c=getchar(); }
}void add(int u,int v,int w)
{to[++tot]=v; nxt[tot]=front[u]; front[u]=tot; val[tot]=w;to[++tot]=u; nxt[tot]=front[v]; front[v]=tot; val[tot]=w;
}inline double X(int i,int j) { return dis[j]-dis[i]; }
inline double Y(int i,int j) { return 1LL*dis[j]*dis[j]+dp[j]-1LL*dis[i]*dis[i]-dp[i]; }void dfs(int x,int y)
{int now_h=head,now_t=tail;int l=head,r=tail-2,mid,tmp=-1;while(l<=r){mid=l+r>>1;if(Y(q[mid],q[mid+1])>=2*dis[x]*X(q[mid],q[mid+1])) tmp=mid,r=mid-1;else l=mid+1;}if(tmp!=-1) head=tmp;else head=tail-1;int j=q[head];dp[x]=1LL*(dis[x]-dis[j])*(dis[x]-dis[j])+P+dp[j];l=head,r=tail-2,tmp=-1;while(l<=r){mid=l+r>>1;if(Y(q[mid],q[mid+1])*X(q[mid+1],x)<=Y(q[mid+1],x)*X(q[mid],q[mid+1])) tmp=mid,l=mid+1;else r=mid-1;}if(tmp!=-1) tail=tmp+2;else tail=head+1;int rr=q[tail];q[tail++]=x;for(int i=front[x];i;i=nxt[i])if(to[i]!=y){dis[to[i]]=dis[x]+val[i];dfs(to[i],x);}head=now_h; q[tail-1]=rr; tail=now_t;
}void clear()
{tot=0;memset(front,0,sizeof(front));
}int main()
{int T;read(T);int n,u,v,w;while(T--){clear();read(n); read(P);for(int i=1;i<n;++i){read(u); read(v); read(w);add(u,v,w);}dp[1]=-P;for(int i=front[1];i;i=nxt[i]){head=0; tail=1;q[0]=1;dis[to[i]]=val[i];dfs(to[i],1);}LL ans=0;for(int i=2;i<=n;++i) ans=max(ans,dp[i]);cout<<ans<<'\n';}
}