#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector,fast-math")
using namespace std;
namespace io {
const int L = (1 << 20) + 1;
char buf[L], *S, *T, c;
char getchar() {
  if (__builtin_expect(S == T, 0)) {
    T = (S = buf) + fread(buf, 1, L, stdin);
    return (S == T ? EOF : *S++);
  }
  return *S++;
}
int inp() {
  int x = 0, f = 1;
  char ch;
  for (ch = getchar(); !isdigit(ch); ch = getchar())
    if (ch == '-') f = -1;
  for (; isdigit(ch); x = x * 10 + ch - '0', ch = getchar())
    ;
  return x * f;
}
unsigned inpu() {
  unsigned x = 0;
  char ch;
  for (ch = getchar(); !isdigit(ch); ch = getchar())
    ;
  for (; isdigit(ch); x = x * 10 + ch - '0', ch = getchar())
    ;
  return x;
}
long long inp_ll() {
  long long x = 0;
  int f = 1;
  char ch;
  for (ch = getchar(); !isdigit(ch); ch = getchar())
    if (ch == '-') f = -1;
  for (; isdigit(ch); x = x * 10 + ch - '0', ch = getchar())
    ;
  return x * f;
}
char B[25], *outs = B + 20, *outr = B + 20;
template <class T>
inline void print(register T a, register char x = 0) {
  if (x) *--outs = x, x = 0;
  if (!a)
    *--outs = '0';
  else
    while (a) *--outs = (a % 10) + 48, a /= 10;
  if (x) *--outs = x;
  fwrite(outs, outr - outs, 1, stdout);
  outs = outr;
}
};  // namespace io
using io ::inp;
using io ::inp_ll;
using io ::inpu;
using io ::print;
using i32 = int;
using i64 = long long;
using u8 = unsigned char;
using u32 = unsigned;
using u64 = unsigned long long;
using f64 = double;
using f80 = long double;
long long power(long long a, long long b, long long p) {
  if (!b) return 1;
  long long t = power(a, b / 2, p);
  t = t * t % p;
  if (b & 1) t = t * a % p;
  return t;
}
long long exgcd(long long a, long long b, long long &x, long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long px, py;
  long long d = exgcd(b, a % b, px, py);
  x = py;
  y = px - a / b * py;
  return d;
}
template <class T>
inline void freshmin(T &a, const T &b) {
  if (a > b) a = b;
}
template <class T>
inline void freshmax(T &a, const T &b) {
  if (a < b) a = b;
}
const int MAXN = 100010;
const int MAXK = 210;
const int MOD = 1000000007;
const f80 MI = f80(1) / MOD;
const int INF = 100001;
int n, k;
int S[MAXK][MAXK];
vector<int> v[MAXN];
int size[MAXN];
int f[MAXN][MAXK], g[MAXN][MAXK], tmp[MAXK];
int ans[MAXK];
void dfs(int x, int p) {
  f[x][0] = 1;
  for (auto y : v[x]) {
    if (y == p) continue;
    dfs(y, x);
    for (int i = 0; i <= k && i <= size[y]; ++i)
      ans[i] = (ans[i] + MOD - g[y][i]) % MOD;
    for (int i = 0; i <= k && i <= size[x] + size[y]; ++i) tmp[i] = 0;
    for (int i = 0; i <= k && i <= size[x]; ++i)
      for (int j = 0; j <= k && j <= size[y]; ++j)
        tmp[i + j] = (tmp[i + j] + (long long)f[x][i] * g[y][j]) % MOD;
    size[x] += size[y];
    for (int i = 0; i <= k && i <= size[x]; ++i) f[x][i] = tmp[i];
  }
  size[x]++;
  for (int i = 0; i <= k && i <= size[x]; ++i) {
    f[x][i] = f[x][i] * 2 % MOD;
    g[x][i] = (f[x][i] + (i ? f[x][i - 1] : 0) - (i == 1)) % MOD;
    ans[i] = (ans[i] + f[x][i]) % MOD;
  }
}
int main() {
  S[0][0] = 1;
  for (int i = 1; i <= 200; ++i)
    for (int j = 1; j <= i; ++j)
      S[i][j] = (S[i - 1][j - 1] + (long long)S[i - 1][j] * j) % MOD;
  n = inp();
  k = inp();
  for (int i = 1; i < n; ++i) {
    int x = inp();
    int y = inp();
    v[x].push_back(y);
    v[y].push_back(x);
  }
  dfs(1, 0);
  int ret = 0;
  for (int i = 0, fact = 1; i <= k; ++i) {
    ret = (ret + (long long)S[k][i] * fact % MOD * ans[i]) % MOD;
    fact = (long long)fact * (i + 1) % MOD;
  }
  cout << ret << endl;
  return 0;
}
