#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = (int)1e9;
const long long LINF = (long long)1e18;
const long double PI = acos((long double)-1);
const long double EPS = 1e-9;
inline long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
inline long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
inline int chkmin(T& a, const T& val) {
  return val < a ? a = val, 1 : 0;
}
template <class T>
inline int chkmax(T& a, const T& val) {
  return a < val ? a = val, 1 : 0;
}
template <class T>
inline T isqrt(T k) {
  T r = sqrt(k) + 1;
  while (r * r > k) r--;
  return r;
}
template <class T>
inline T icbrt(T k) {
  T r = cbrt(k) + 1;
  while (r * r * r > k) r--;
  return r;
}
inline void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
inline void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
inline int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(long double x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(long double x, long double y) { return sign(x - y); }
template <class T, T p, class mul, class dvd>
struct FiniteField {
  T x;
  template <class G>
  T normalize(G x) {
    if (x >= 0 && x < p) return x;
    x %= p;
    if (x < 0)
      x += p;
    else if (x >= p)
      x -= p;
    return x;
  }
  FiniteField() { x = 0; }
  template <class G>
  FiniteField(const G& y) {
    x = normalize(y);
  }
  FiniteField(const FiniteField& rhs) { x = rhs.x; }
  template <class G>
  FiniteField operator()(const G& y) {
    x = normalize(y);
    return *this;
  }
  template <class G>
  FiniteField operator=(const G& y) {
    x = normalize(y);
    return *this;
  }
  FiniteField operator++(int) {
    FiniteField res = *this;
    if ((++x) >= p) x -= p;
    return res;
  }
  FiniteField operator++() {
    if ((++x) >= p) x -= p;
    return *this;
  }
  FiniteField operator--(int) {
    FiniteField res = *this;
    if ((--x) < 0) x += p;
    return res;
  }
  FiniteField operator--() {
    if ((--x) < 0) x += p;
    return *this;
  }
  template <class G>
  FiniteField operator+=(const G& y) {
    if ((x += normalize(y)) >= p) x -= p;
    return *this;
  }
  template <class G>
  FiniteField operator-=(const G& y) {
    if ((x -= normalize(y)) < 0) x += p;
    return *this;
  }
  FiniteField operator+=(const FiniteField& rhs) {
    if ((x += rhs.x) >= p) x -= p;
    return *this;
  }
  FiniteField operator-=(const FiniteField& rhs) {
    if ((x -= rhs.x) < 0) x += p;
    return *this;
  }
  FiniteField operator+(const FiniteField& rhs) const {
    FiniteField res;
    res.x = x + rhs.x;
    if (res.x >= p) res.x -= p;
    return res;
  }
  FiniteField operator-(const FiniteField& rhs) const {
    FiniteField res;
    res.x = x - rhs.x;
    if (res.x < 0) res.x += p;
    return res;
  }
  template <class G>
  FiniteField operator*=(const G& y) {
    x = mul()(x, normalize(y), p);
    return *this;
  }
  template <class G>
  FiniteField operator/=(const G& y) {
    x = dvd()(x, normalize(y), p);
    return *this;
  }
  template <class G>
  FiniteField operator*(const G& y) const {
    FiniteField res;
    res.x = mul()(x, res.normalize(y), p);
    return res;
  }
  template <class G>
  FiniteField operator/(const G& y) const {
    FiniteField res;
    res.x = dvd()(x, res.normalize(y), p);
    return res;
  }
  FiniteField operator*(const FiniteField& rhs) const {
    FiniteField res;
    res.x = mul()(x, rhs.x, p);
    return res;
  }
  FiniteField operator/(const FiniteField& rhs) const {
    FiniteField res;
    res.x = dvd()(x, rhs.x, p);
    return res;
  }
  template <class G>
  friend FiniteField operator*(const G& y, const FiniteField& rhs) {
    FiniteField res;
    res.x = res.normalize(y);
    return res * rhs;
  }
  template <class G>
  friend FiniteField operator/(const G& y, const FiniteField& rhs) {
    FiniteField res;
    res.x = res.normalize(y);
    return res / rhs;
  }
  template <class G>
  FiniteField operator^=(G k) {
    if (k == 0) {
      x = 1;
      return *this;
    }
    T t = x;
    k--;
    while (k > 0) {
      if (k & 1) x = mul()(x, t, p);
      t = mul()(t, t, p);
      k >>= 1;
    }
    return *this;
  }
  template <class G>
  FiniteField operator^(G k) const {
    if (k == 0) return 1;
    T r = x, t = x;
    k--;
    while (k > 0) {
      if (k & 1) r = mul()(r, t, p);
      t = mul()(t, t, p);
      k >>= 1;
    }
    return r;
  }
  friend ostream& operator<<(ostream& os, const FiniteField& rhs) {
    os << rhs.x;
    return os;
  }
};
template <class T>
class mul {
 public:
  T operator()(const T& x, const T& y, const T& p) {
    return (long long)x * y % p;
  }
};
template <class T>
class dvd {
 public:
  T operator()(const T& x, const T& y, const T& p) {
    pair<T, T> r = euclid(y, p);
    return mul<T>()(x, (r.first % p + p) % p, p);
  }

 private:
  pair<T, T> euclid(T a, T b) {
    if (b == 0) return make_pair(1, 0);
    pair<T, T> r = euclid(b, a % b);
    return make_pair(r.second, r.first - a / b * r.second);
  }
};
typedef FiniteField<int, (int)1e9 + 7, mul<int>, dvd<int> > FF;
const int maxn = 1000000 + 10;
const int maxk = 2000 + 10;
const int magic = 22;
int n, m, k, s;
int a[maxk];
int b[maxk];
FF fac[maxn];
FF ifac[maxn];
FF f[maxk][magic];
FF binom(int a, int b) {
  if (!a || a == b) return FF(1);
  return fac[b] * ifac[a] * ifac[b - a];
}
void solve() {
  fac[0] = 1;
  for (int i = (1); i < (maxn); i++) fac[i] = fac[i - 1] * i;
  for (int i = (0); i < (maxn); i++) ifac[i] = 1 / fac[i];
  cin >> n >> m >> k >> s;
  vector<pair<int, int> > vx;
  int tot = 0;
  for (int i = (0); i < (k); i++) {
    cin >> a[i] >> b[i];
    if (!a[i] && !b[i]) {
      tot++;
    } else if (a[i] == n && b[i] == m) {
      tot++;
    } else {
      vx.push_back(make_pair(a[i], b[i]));
    }
  }
  vx.push_back(make_pair(1, 1)), vx.push_back(make_pair(n, m));
  sort((vx).begin(), (vx).end());
  f[0][0] = 1;
  for (int i = (1); i < (int((vx).size())); i++) {
    int u = vx[i].first;
    int v = vx[i].second;
    f[i][0] = binom(u - 1, u + v - 2);
    for (int k = (1); k < (magic); k++) {
      for (int j = (1); j < (i); j++) {
        int p = vx[i].first - vx[j].first;
        int q = vx[i].second - vx[j].second;
        if (p >= 0 && q >= 0) {
          f[i][k] += f[j][k - 1] * binom(p, p + q);
        }
      }
    }
    for (int k = (0); k < (magic - 1); k++) {
      f[i][k] -= f[i][k + 1];
    }
  }
  FF ans = 0;
  int t = int((vx).size());
  for (int i = (0); i < (magic); i++) {
    FF k = f[t - 1][i];
    int tmp = s;
    for (int it = (0); it < (i + tot); it++) tmp = (tmp + 1) / 2;
    ans += tmp * k;
  }
  ans = ans / binom(n - 1, n + m - 2);
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  solve();
  return 0;
}
