#include <stdio.h>
const long long mod = 1000000007;
long long fpow(long long a, long long p)
{
a = (a % mod + mod) % mod;
p = (p % (mod - 1) + mod - 1) % (mod - 1);
long long r = 1;
while (p){
if (p & 1) r = r * a % mod;
a = a * a % mod;
p >>= 1;
}
return r;
}
int main()
{
int P,Q,N,K; scanf ("%d %d %d %d",&P,&Q,&N,&K);
if (K == 0) puts("0");
else if (K == N) puts("1");
else if (Q == 0) puts("1");
else if (Q == P) puts("0");
else if (Q * 2 == P) printf ("%lld\n",K*fpow(N,-1));
else{
long long v[101];
long long pr = Q * fpow(P,-1) % mod, rv = fpow(1-pr,-1);
v[0] = 0; v[1] = 1;
for (int i=2;i<=N;i++) v[i] = ((v[i-1] - pr * v[i-2]) % mod * rv % mod + mod) % mod;
printf ("%lld\n",v[K]*fpow(v[N],-1)%mod);
}
return 0;
}
