#include<bits/stdc++.h>

using namespace std;
using ll = long long;

ll n, k;
vector<vector<int>> hen;

#define MOD 1000000007
template<int mod>
struct ModInt{
   int x;
   ModInt():x(0){}
   ModInt(long long y):x(y>=0?y%mod:(mod-(-y)%mod)%mod){}
   ModInt &operator+=(const ModInt &p){
       if((x+=p.x)>=mod)x-=mod;
       return *this;
   }
   ModInt &operator-=(const ModInt &p){
       if((x+=mod-p.x)>=mod)x-=mod;
       return *this;
   }
   ModInt &operator*=(const ModInt &p){
       x=(int)(1LL*x*p.x%mod);
       return *this;
   }
   ModInt &operator/=(const ModInt &p){
       *this*=p.inverse();
       return *this;
   }
   ModInt &operator^=(long long p){
       ModInt res = 1;
       for (; p; p >>= 1) {
           if (p & 1) res *= *this;
           *this *= *this;
       }
       return *this = res;
   }
   ModInt operator-()const{return ModInt(-x);}
   ModInt operator+(const ModInt &p)const{return ModInt(*this)+=p;}
   ModInt operator-(const ModInt &p)const{return ModInt(*this)-=p;}
   ModInt operator*(const ModInt &p)const{return ModInt(*this)*=p;}
   ModInt operator/(const ModInt &p)const{return ModInt(*this)/=p;}
   ModInt operator^(long long p)const{return ModInt(*this)^=p;}
   bool operator==(const ModInt &p)const{return x==p.x;}
   bool operator!=(const ModInt &p)const{return x!=p.x;}
   explicit operator int() const { return x; }
   ModInt operator=(const int p) {x = p; return ModInt(*this);}
   ModInt inverse()const{
       int a=x,b=mod,u=1,v=0,t;
       while(b>0){
           t=a/b;
           a-=t*b;
           std::swap(a,b);
           u-=t*v;
           std::swap(u,v);
       }
       return ModInt(u);
   }
   friend std::ostream &operator<<(std::ostream &os,const ModInt<mod> &p){
       return os<<p.x;
   }
   friend std::istream &operator>>(std::istream &is,ModInt<mod> &a){
       long long x;
       is>>x;
       a=ModInt<mod>(x);
       return (is);
   }
};
typedef ModInt<MOD> mint;
 
struct MComb {
   std::vector<mint> fact;
   std::vector<mint> inversed;
   MComb(int n) { // O(n+log(mod))
       fact = std::vector<mint>(n+1,1);
       for (int i = 1; i <= n; i++) fact[i] = fact[i-1]*mint(i);
       inversed = std::vector<mint>(n+1);
       inversed[n] = fact[n] ^ (MOD-2);
       for (int i = n - 1; i >= 0; i--) inversed[i]=inversed[i+1]*mint(i+1);
   }
   mint ncr(int n, int r) {
        if (n < r) return 0;
        if (n < 0 || r < 0) return 0;
       return (fact[n] * inversed[r] * inversed[n-r]);
   }
   mint npr(int n, int r) {
        if (n < r) return 0;
        if (n < 0 || r < 0) return 0;
       return (fact[n] * inversed[n-r]);
   }
   mint nhr(int n, int r) {
       assert(n+r-1 < (int)fact.size());
       return ncr(n+r-1, r);
   }
};
MComb comb(200000);

mint res;
void dfs(int v, int par) {
    res *= comb.npr(k - (par != -1) - 1, hen[v].size() - (par != -1));
    for(auto i : hen[v]) {
        if(i == par)continue;
        dfs(i, v);
    }
}

int main()
{
    cin >> n >> k;
    hen.resize(n);
    for(int i = 0; i < n - 1; i++) {
        int a, b; cin >> a >> b; a--, b--;
        hen[a].push_back(b);
        hen[b].push_back(a);
    }
    res = k;
    dfs(0, -1);
    cout << res << endl;
}

Measured memory_bytes: 10752