#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i ++)
#define irep(i,n) for (int i = (int)(n) - 1;i >= 0;--i)
using namespace std;
using ll = long long;
using PL = pair<ll,ll>;
using P = pair<int,int>;
constexpr int INF = 1000000000;
constexpr long long HINF = 1000000000000000;
constexpr long long MOD = 1000000007;// = 998244353;
constexpr double EPS = 1e-4;
constexpr double PI = 3.14159265358979;

struct UnionFind {
    int N;
    vector<int> parents;

    UnionFind(int _N) : N(_N){
        parents.assign(N,-1);
    }

    int find(int x) { //xの親を返す
        if (parents[x] < 0) return x;
        return parents[x] = find(parents[x]);
    }
    
    void unite(int x, int y) {  //xとyの含むグループを併合
        int px = find(x);
        int py = find(y);
        if (parents[px] > parents[py]) swap(px,py); 
        if (px != py) {
            parents[px] += parents[py];
            parents[py] = px;
        }     
    }

    bool same(int x, int y) { //x,yが同じグループにいるか判定
        return find(x) == find(y);
    }

    int size(int x) { //xと同じグループのメンバーの個数
        return -parents[find(x)];
    }
    
    vector<int> root() {//ufの根を列挙
        vector<int> res;
        for (int i = 0; i < N; i ++) {
            if (parents[i] < 0) res.push_back(i);
        }
        return res;
    }

    int group_count() { //ufのグループの数を数える
        int cnt = 0;
        for (int i = 0; i < N; i ++) {
            if (parents[i] < 0) cnt ++;
        }
        return cnt;
    }
};


template<int Modulus> 
struct ModInt {
    long long x;
    ModInt(long long x = 0) :x((x%Modulus + Modulus)%Modulus) {}
    constexpr ModInt &operator+=(const ModInt a) {if ((x += a.x) >= Modulus) x -= Modulus; return *this;}
    constexpr ModInt &operator-=(const ModInt a) {if ((x += Modulus - a.x) >= Modulus) x -= Modulus; return *this;}
    constexpr ModInt &operator*=(const ModInt a) {(x *= a.x) %= Modulus; return *this;}
    constexpr ModInt &operator/=(const ModInt a) {return *this *= a.inverse();}

    constexpr ModInt operator+(const ModInt a) const {return ModInt(*this) += a.x;}
    constexpr ModInt operator-(const ModInt a) const {return ModInt(*this) -= a.x;}
    constexpr ModInt operator*(const ModInt a) const {return ModInt(*this) *= a.x;}
    constexpr ModInt operator/(const ModInt a) const {return ModInt(*this) /= a.x;}
    
    friend constexpr ostream& operator<<(ostream& os,const ModInt<Modulus>& a) {return os << a.x;}
    friend constexpr istream& operator>>(istream& is,ModInt<Modulus>& a) {return is >> a.x;}
    
    ModInt inverse() const {// x ^ (-1) 
        long long a = x,b = Modulus,p = 1,q = 0;
        while (b) {long long d = a/b; a -= d*b; swap(a,b); p -= d*q; swap(p,q);}
        return ModInt(p);
    }
    ModInt pow(long long N) {// x ^ N 
        ModInt a = 1;
        while (N) {
            if (N&1) a *= *this;
            *this *= *this;
            N >>= 1;
        }
        return a;
    }
};

using mint = ModInt<1000000007>;

mint ans = 0;
int N;
ll X;
vector<vector<P>> G;

int dfs(int v,int pa = -1) {
    int cnt = 1;
    for (const P &p:G[v]) {
        if (p.first == pa) continue; 
        int c = dfs(p.first,v);
        ans += mint(N - c) * mint(c) * mint(X).pow(p.second);
        cnt += c;
    }
    return cnt;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int M;
    cin >> N >> M >> X;
    
    UnionFind uf(N);
    G.resize(N);
    rep(i,M) {
        int a,b,c;
        cin >> a >> b >> c;
        --a; --b;
        if (uf.same(a,b)) continue;
        uf.unite(a,b);
        G[a].emplace_back(b,c);
        G[b].emplace_back(a,c);
    }
    dfs(0);
    cout << ans << '\n';
    return 0;
}