using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m, x) = (c[0], c[1], c[2]);
        var map = NArr(m);
        var tree = new List<(int to, int len)>[n];
        for (var i = 0; i < n; ++i) tree[i] = new List<(int to, int len)>();
        var uf = new UnionFindTree(n);
        for (var i = 0; i < m; ++i)
        {
            var u = map[i][0] - 1;
            var v = map[i][1] - 1;
            if (uf.Unite(u, v))
            {
                tree[u].Add((v, map[i][2]));
                tree[v].Add((u, map[i][2]));
            }
        }
        var size = new int[n];
        WriteLine(DFS(0, -1, n, x, tree, size));
    }
    static int mod = 1_000_000_007;
    static long DFS(int cur, int prev, int n, int x, List<(int to, int len)>[] tree, int[] size)
    {
        var ans = 0L;
        var stmp = 1;
        foreach (var next in tree[cur])
        {
            if (prev == next.to) continue;
            ans = (ans + DFS(next.to, cur, n, x, tree, size)) % mod;
            stmp += size[next.to];
            ans = (ans + Exp(x, next.len, mod) * size[next.to] % mod * (n - size[next.to]) % mod) % mod;
        }
        size[cur] = stmp;
        return ans;
    }
    static long Exp(long n, long p, int mod)
    {
        long _n = n % mod;
        var _p = p;
        var result = 1L;
        if ((_p & 1) == 1) result *= _n;
        while (_p > 0)
        {
            _n = _n * _n % mod;
            _p >>= 1;
            if ((_p & 1) == 1) result = result * _n % mod;
        }
        return result;
    }
    class UnionFindTree
    {
        int[] roots;
        public UnionFindTree(int size)
        {
            roots = new int[size];
            for (var i = 0; i < size; ++i) roots[i] = -1;
        }
        public int GetRoot(int a)
        {
            if (roots[a] < 0) return a;
            return roots[a] = GetRoot(roots[a]);
        }
        public bool IsSameTree(int a, int b)
        {
            return GetRoot(a) == GetRoot(b);
        }
        public bool Unite(int a, int b)
        {
            var x = GetRoot(a);
            var y = GetRoot(b);
            if (x == y) return false;
            if (-roots[x] < -roots[y]) { var tmp = x; x = y; y = tmp; }
            roots[x] += roots[y];
            roots[y] = x;
            return true;
        }
        public int GetSize(int a)
        {
            return -roots[GetRoot(a)];
        }
    }
}