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

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int,int> ii;
typedef pair<ll,ll> llll;
typedef pair<double,double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a)  int((a).size())
#define pb  push_back
#define eb  emplace_back
#define FOR(var,from,to) for(int var=(from);var<=(to);++var)
#define rep(var,n)  for(int var=0;var<(n);++var)
#define rep1(var,n)  for(int var=1;var<=(n);++var)
#define repC2(vari,varj,n)  for(int vari=0;vari<(n)-1;++vari)for(int varj=vari+1;varj<(n);++varj)
#define ALL(c)  (c).begin(),(c).end()
#define RALL(c)  (c).rbegin(),(c).rend()
#define tr(i,c)  for(auto i=(c).begin(); i!=(c).end(); ++i)
#define found(s,e)  ((s).find(e)!=(s).end())
#define mset(arr,val)  memset(arr,val,sizeof(arr))
#define mid(x,y) ((x)+((y)-(x))/2)
#define IN(x,a,b) ((a)<=(x)&&(x)<=(b))
#define cons make_pair

#define PQ(T) priority_queue<T>
#define RPQ(T) priority_queue<T,vector<T>,greater<T>>

template<class T> inline void amin(T & a, T const & b) { a = min(a, b); }
template<class T> inline void amax(T & a, T const & b) { a = max(a, b); }

inline ll square(ll x) { return x * x; }
inline ll gcd(ll a, ll b) { while(a) swap(a, b%=a); return b; }
template <typename T>
inline T mod(T a, T b) { return ((a % b) + b) % b; }


const ll MOD=1000000007LL;

ll ADD(ll x, ll y) { return (x+y) % MOD; }
ll SUB(ll x, ll y) { return (x-y+MOD) % MOD; }
ll MUL(ll x, ll y) { return x*y % MOD; }
ll POW(ll x, ll e) { ll v=1; for(; e; x=MUL(x,x), e>>=1) if (e&1) v = MUL(v,x); return v; }
ll DIV(ll x, ll y) { /*assert(y%MOD!=0);*/ return MUL(x, POW(y, MOD-2)); }

#define INTSPACE 12
char _buf[INTSPACE*1000000 + 3];

int loadint() {
    if (fgets(_buf, INTSPACE+3, stdin)==NULL) return 0;
    return atoi(_buf);
}

int loadvec(vector<int>& v, int N=-1) {
    if (N == 0) {
        v.clear();
        return 0;
    }
    if (N == -1) {
        N = loadint();
        if (N==0) return 0;
    }
    int bufsize = INTSPACE*N + 3;
    if (fgets(_buf, bufsize, stdin)==NULL) return 0;
    v.resize(N);

    int i=0;
    bool last = false;
    for (char *p=&_buf[0]; ;) {
        char *q = p;
        while (*q > ' ') ++q;
        if (*q == 0x0D || *q == 0x0A) last = true;
        *q = 0;
        v[i++] = atoi(p);
        if (last || i == N) break;
        p = q+1;
    }
    return i;
}
void read_cr() {
    fgets(_buf, 256, stdin);
}


ll fact[100001];
ll nCk(int n, int k) {
    ll numer = fact[n];
    ll denom = MUL(fact[n-k], fact[k]);
    ll x = DIV(numer ,denom);
    return x;
}

ll solve(int N, int K, vi& u, vi& v) {
    vvi nxt(N);
    rep(i,N-1){
        nxt[ u[i] ].pb( v[i] );
        nxt[ v[i] ].pb( u[i] );
    }
    vi visited(N, 0);
    queue<ii> q;
    q.emplace(0,0);
    ll ans = K;
    while (!q.empty()) {
        int u = q.front().first, lv = q.front().second;
        q.pop();

        visited[u] = 1;
        int cnt = 0;
        for (int v: nxt[u]){
            if (!visited[v]) {
                ++cnt;
                q.emplace(v,lv+1);
            }
        }
        int n = (lv==0) ? K-1 : K-2;
        if (n < cnt) return 0;
        ll pat = MUL(nCk(n, cnt), fact[cnt]);
        ans = MUL(ans, pat);
    }

    return ans;
}

int main() {
    fact[0] = fact[1] = 1;
    for (int n=2; n<=100000; ++n){
        fact[n] = (fact[n-1] * n) % MOD;
    }

    int N, K; scanf("%d %d%*c", &N, &K);
    vi u(N-1), v(N-1);
    rep(i,N-1){
        scanf("%d %d%*c", &u[i], &v[i]);
        --u[i]; --v[i];
    }
    cout << solve(N,K,u,v) << endl;
    return 0;
}


Measured memory_bytes: 8824