#pragma GCC optimize("O3")
#include <bits/stdc++.h> 
using namespace std;
using ll=long long;
using P=pair<ll,ll>;
template<class T> using V=vector<T>; 
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
const ll inf=(1e18);
//const ll mod=998244353;
const ll mod=1000000007;
ll GCD(ll a,ll b) {return b ? GCD(b,a%b):a;}
ll LCM(ll c,ll d){return c/GCD(c,d)*d;}
struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}} __init;
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
struct mint{
    using ull=unsigned long long int;
    ull v;
    mint(ll vv=0){s(vv%mod+mod);}
    mint& s(ull vv){
        v=vv<mod?vv:vv-mod;
        return *this;
    }
    //オーバーロード
    mint operator-()const{return mint()-*this;}//符号反転
    mint&operator+=(const mint&val){return s(v+val.v);}
    mint&operator-=(const mint&val){return s(v+mod-val.v);}
    mint&operator*=(const mint&val){
        v=ull(v)*val.v%mod;
        return *this;
    }
    mint&operator/=(const mint&val){return *this*=val.inv();}
    mint operator+(const mint&val){return mint(*this)+=val;}
    mint operator-(const mint&val){return mint(*this)-=val;}
    mint operator*(const mint&val){return mint(*this)*=val;}
    mint operator/(const mint&val){return mint(*this)/=val;}
    mint pow(ull n)const{
        mint res(1),x(*this);
        while(n){
            if(n&1)res*=x;
            x*=x;
            n>>=1;
        }
        return res;
    }
     mint inv()const{return pow(mod-2);}
    //拡張ユークリッドの互除法
    /* mint inv()const{
        int x,y;
        int g=extgcd(v,mod,x,y);
        assert(g==1);
        if(x<0)x+=mod;
        return mint(x);
    }*/
    friend ostream& operator<<(ostream&os,const mint&val){
        return os<<val.v;
    }//出力
    bool operator<(const mint&val)const{return v<val.v;}
    bool operator==(const mint&val)const{return v==val.v;}
    bool operator>(const mint&val)const{return v>val.v;}
};
struct edge{
    ll to,cost;
    edge(ll to,ll cost):to(to),cost(cost) {}
};
vector<vector<edge>> g;
ll n,m;
class UF{
public:
	vector<int> par,num;
	int find(int v){
		return (par[v]==v)? v: (par[v]=find(par[v]));
	}
	explicit UF(int N):par(N),num(N,1){
		iota(all(par),0);
	}
	void unite(int u,int v){
		u=find(u),v=find(v);
		if(u==v)return;
		if(num[u]<num[v])swap(u,v);
		num[u]+=num[v];
		par[v]=u;
	}
	bool same(int u,int v){
		return find(u)==find(v);
	}
	bool ispar(int v){
		return v=find(v);
	}
	int size(int v){
		return num[find(v)];
	}
};
mint ans=0;
V<ll> cnt;
ll D;
void dfs(int cur,int par){
    for(edge &e:g[cur]){
        if(e.to==par)continue;
        dfs(e.to,cur);
    }
    for(edge &e:g[cur]){
        if(e.to==par)continue;
        ans+=mint(D).pow(e.cost)*mint((cnt[e.to])*(n-cnt[e.to]));
        cnt[cur]+=cnt[e.to];
    }
    cnt[cur]++;
}
int main(){
    cin>>n>>m>>D;
    cnt.assign(n,0);
    g.resize(n);
    UF uf(n);
    ll x,y,z;
    for(int i=0;i<m;i++){
        cin>>x>>y>>z;
        x--;y--;
        if(uf.same(x,y))continue;
        uf.unite(x,y);
        g[x].emplace_back(y,z);
        g[y].emplace_back(x,z);
    }
     dfs(0,-1);
    cout<<ans<<"\n";
}