var GET=(function(){function f(s){return new g(s);}function g(s){this._s=s.trim().split("\n");this._y=0;}g.prototype.a=function(f){var s=this._s, y=this._y, r;if(typeof s[y]==="string")s[y]=s[y].split(" ").reverse();r=s[y].pop();if(!s[y].length)this._y++;return f?r:+r;};g.prototype.l=function(f){var s=this._s[this._y++].split(" ");return f?s:s.map(a=>+a);};g.prototype.m=function(n,f){var r=this._s.slice(this._y,this._y+=n).map(a=>a.split(" "));return f?r:r.map(a=>a.map(a=>+a));};g.prototype.r=function(n,f){var r=this._s.slice(this._y,this._y+=n);return f?r:r.map(a=>+a);};return f;})();
var o=GET(require("fs").readFileSync("/dev/stdin","utf8"));
function xArray(v){var a=arguments,l=a.length,r="Array(a["+--l+"]).fill(0).map(x=>{return "+v+";})";while(--l)r="Array(a["+l+"]).fill(0).map(x=>"+r+")";return eval(r);}
var mod = 1e9+7;

console.log(main());
function main(){
  var n = o.a();
  var k = o.a();
  var e = xArray("[]",n);
  var ans = k;
  for(var i = 0; i < n-1; i++){
    var a = o.a()-1, b = o.a()-1;
    e[a].push(b);
    e[b].push(a);
  }
  var q = [], q2 = [0], d = 1;
  var m = xArray(0,n);
  m[0] = 1;
  while(q2.length){
    q = q2;
    var q2 = [];
    while(q.length){
      var v = q.pop();
      var z = 0;
      if(d > 1)z = 1;
      for(var i = 0; i < e[v].length-z; i++){
        ans *= k-d-i;
        ans %= mod;
      }
      for(var V of e[v]){
        if(m[V])continue;
        q2.push(V);
        m[V] = 1;
      }
    }
    if(d < 2)d++;
  }
  return 0+ans;
}