#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=double;
#define FOR(i,a,b) for(ll i=a;i<(ll)b;++i)
#define F(n) FOR(i,0,n)
#define FF(n) FOR(j,0,n)
#define aa first
#define bb second
#define PB push_back
#define EQ(a,b) (fabs(a-b)<=(fabs(a+b)*EPS))
#define MOD 1000000007

inline ll d(ll n) {
  return n >= MOD ? n%MOD : n;
}

inline ll mpow(ll b, ll ex=MOD-2) {
  if (b==1) return 1;
  ll r = 1;
  while (ex) {
    if(ex&1)r = (r*b)%MOD;
    ex >>= 1;
    b = (b*b)%MOD;
  }
  return r;
}

ll Cmod(ll n, ll k, ll p=MOD) {
  ll top = 1;
  ll bottom = 1;
  for (ll i = n; i > k; -- i) {
    top *= i;
    top %= p;
  }
  for (ll i = n-k; i > 0; -- i) {
    bottom *= i;
    bottom %= p;
  }
  return ((top % p) * (mpow(bottom, p-2) % p)) % p;
}

int main(){
	ios::sync_with_stdio(0);cout.tie(0);cin.tie(0);
  ll a, b, k, c;
  cin >> a >> b >> k >> c;
  if (a != c && b != c) {
    cout << 0 << endl;
    return 0;
  }
  ll res = 0;
  for (int i = 1; i <= k; ++ i) {
    res += d(d(Cmod(k, i) * i));
    res = d(res);
    //cout << Cmod(k, i) << endl;
  }
  cout << res << endl;

	return 0;
}