using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	const long inf=long.MaxValue-1;
	static List<ValueTuple<int,int>>[] li;
	static bool[] b;
	static Mint[] d;
	static int[] pa;
	static long x;
	static int n;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Ia;
		var g=new int[s[1]][];
		n=s[0];
		int m=n-1;
		x=s[2];
		for(int i = 0;i<s[1];i++) {g[i]=sc.Ia;}
		Uf uf=new Uf(n+1);
		li=new List<ValueTuple<int,int>>[n+1];
		b=new bool[n+1];
		d=new Mint[n+1];
		pa=new int[n+1];
		for(int i=1;i<=n;i++){
			li[i]=new List<ValueTuple<int,int>>();
		}
		for(int i = 0;i<s[1];i++) {
			if(!uf.Same(g[i][0],g[i][1])){
				uf.Union(g[i][0],g[i][1]);
				li[g[i][0]].Add(ValueTuple.Create(g[i][1],g[i][2]));
				li[g[i][1]].Add(ValueTuple.Create(g[i][0],g[i][2]));
			}
		}
		int o=1;
		Fu(o);
		b=new bool[n+1];
		Fu2(o);
		Mint ans=0;
		for(int i = 1;i<=n;i++) {ans+=d[i];}
		Console.WriteLine("{0}",ans/2);
	}
	static int Fu2(int a){
		b[a]=true;
		for(int i=0;i<li[a].Count;i++){
			if(!b[li[a][i].Item1]){
				var c=Fp(x,li[a][i].Item2);
				d[li[a][i].Item1]+=d[a]-d[li[a][i].Item1]-c*pa[li[a][i].Item1]+c*(n-pa[li[a][i].Item1]);
				Fu2(li[a][i].Item1);
			}
		}
		return 0;
	}
	static int Fu(int a){
		b[a]=true;
		var p=1;
		for(int i=0;i<li[a].Count;i++){
			if(!b[li[a][i].Item1]){
				var k=Fu(li[a][i].Item1);
				var c=Fp(x,li[a][i].Item2);
				p+=k;
				d[a]+=c*k;
				d[a]+=d[li[a][i].Item1];
			}
		}
		return pa[a]=p;
	}
	static long Fp(long x,long e){
		long r=1;
		while(e>0){
			if((e&1)>0){r*=x;r%=mod;}
			x=(x*x)%mod;
			e>>=1;
		}
		return r;
	}
}
public struct Mint{
	const int mod=(int)1e9+7;
	private long d;
	public Mint(long d){this.d=d;}
	public static implicit operator Mint(long d){return new Mint(d%mod);}
	public static implicit operator bool(Mint d){return (int)d!=0;}
	public static explicit operator long(Mint d){return d.d;}
	public override string ToString(){return d.ToString();}
	public static Mint operator+(Mint a,long b){a.d=(a.d+b)%mod;return a;}
	public static Mint operator+(Mint a,Mint b){a.d=(a.d+b.d)%mod;return a;}
	public static Mint operator-(Mint a,long b){a.d=(mod+a.d-b)%mod;return a;}
	public static Mint operator-(Mint a,Mint b){a.d=(mod+a.d-b.d)%mod;return a;}
	public static Mint operator*(Mint a,long b){a.d=(a.d*b)%mod;return a;}
	public static Mint operator*(Mint a,Mint b){a.d=(a.d*b.d)%mod;return a;}
	public static Mint operator/(Mint a,long b){a.d=(a.d*Mi(b))%mod;return a;}
	public static Mint operator/(Mint a,Mint b){a.d=(a.d*Mi(b.d))%mod;return a;}
	private static long Mi(long a){
		a=(a+mod)%mod;
		long b=mod,u=1,v=0;
		while(b>0){
			long t=a/b;
			a-=t*b;(a,b)=(b,a);
			u-=t*v;(u,v)=(v,u);
		}
		u%=mod;
		if(u<0){u+=mod;}
		return u%mod;
	}
}
public class Uf{
	private int[] arr,hi;
	public int all;
	public Uf(int n){
		arr=new int[n];
		hi=new int[n];
		all=n;
		for(int i=0;i<n;i++){arr[i]=-1;}
	}
	public void Union(int a,int b){
		a=Root(a);
		b=Root(b);
		if(a!=b){
			if(hi[a]<hi[b]){(a,b)=(b,a);}
			arr[a]+=arr[b];
			hi[a]=Max(hi[a],hi[b]+1);
			arr[b]=a;
			all--;
		}
	}
	public bool Same(int a,int b){return Root(a)==Root(b);}
	public int Size(int a){return -arr[Root(a)];}
	public int Root(int a){return arr[a]<0?a:arr[a]=Root(arr[a]);}
}
public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}