#include "bits/stdc++.h"
using namespace std;

//#define int long long

#define ll long long
#define rep(i,n) for(ll i = 0; i < (n); i++)
#define P pair<ll,ll>
#define ld long double
ll INF = (1LL << 60);
int mod = 1000000007; struct mint {
	ll x; // typedef long long ll;
	mint(ll x = 0) :x((x%mod + mod) % mod) {}
	mint operator-() const { return mint(-x); }
	mint& operator+=(const mint a) {
		if ((x += a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator-=(const mint a) {
		if ((x += mod - a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator*=(const mint a) {
		(x *= a.x) %= mod;
		return *this;
	}
	mint operator+(const mint a) const {
		mint res(*this);
		return res += a;
	}
	mint operator-(const mint a) const {
		mint res(*this);
		return res -= a;
	}
	mint operator*(const mint a) const {
		mint res(*this);
		return res *= a;
	}
	mint pow(ll t) const {
		if (!t) return 1;
		mint a = pow(t >> 1);
		a *= a;
		if (t & 1) a *= *this;
		return a;
	}

	// for prime mod
	mint inv() const {
		return pow(mod - 2);
	}
	mint& operator/=(const mint a) {
		return (*this) *= a.inv();
	}
	mint operator/(const mint a) const {
		mint res(*this);
		return res /= a;
	}
};
istream& operator>>(istream& is, mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }
struct UnionFind {
	vector<ll>p;
	UnionFind() {}
	UnionFind(ll n) {
		p.resize(n, -1);
	}
	ll find(ll x) {
		if (p[x] == -1)return x;
		else return p[x] = find(p[x]);
	}
	void unite(ll x, ll y) {
		x = find(x), y = find(y);
		if (x == y)return;
		p[x] = y;
	}
};
struct Edge {
	ll a, b, cost;
};
bool comp_e(const Edge &e1, const Edge &e2) {
	return e1.cost < e2.cost;
}
vector<vector<P>>AfterGraph;
struct Kruskal {
	UnionFind uf;
	ll sum;
	vector<Edge>edges;
	ll n;
	Kruskal(const vector<Edge> &edges_, ll n_) : edges(edges_), n(n_) {
		sort(edges.begin(), edges.end(), comp_e);
		uf = UnionFind(n);
		sum = 0;
		vector<ll> costs;
		for (auto e : edges) {
			if (uf.find(e.a) != uf.find(e.b)) {
				uf.unite(e.a, e.b);
				AfterGraph[e.a].push_back({ e.b, e.cost });
				AfterGraph[e.b].push_back({ e.a,e.cost });
				costs.push_back(e.cost);
				sum += e.cost;
			}
		}
	}

};
vector<ll>subtree_size;
void dfs(const vector<vector<P>> &G, ll v, ll p, ll now) {
	for (auto nv : G[v]) {
		if (nv.first == p)continue;
		dfs(G, nv.first, v, now + 1);
	}
	subtree_size[v] = 1;
	for (auto c : G[v]) {
		if (c.first == p)continue;
		subtree_size[v] += subtree_size[c.first];
	}
}
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	ll N, M, X; cin >> N >> M >> X;
	AfterGraph.resize(N);
	subtree_size.resize(N);
	vector<Edge>G(M);
	rep(i, M) {
		ll x, y, z; cin >> x >> y >> z; x--; y--;
		Edge e = { x,y,z };
		G[i] = e;
	}
	Kruskal tmp(G, N);
	dfs(AfterGraph, 0, -1, 0);
	
	mint ans = 0;
	rep(i, N) {
		for (auto v : AfterGraph[i]) {
			mint now = mint(X).pow(v.second);
			ll idx = 0;
			if (subtree_size[i] > subtree_size[v.first]) {
				idx = v.first;
			}
			else idx = i;
			now *= subtree_size[idx];
			now *= (N - subtree_size[idx]);
			ans += now;
		}
	}
	ans /= 2;
	cout << ans << endl;

	return 0;
}