//  Copyright 2020 Nikita Golikov

#include <bits/stdc++.h>

using namespace std;

using i64 = int64_t;
using ui64 = uint64_t;

#ifdef GOLIKOV
mt19937_64 rng(566);
#else
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
#endif

template <typename T>
T rnd_helper(T from, T to, true_type) {
  return uniform_int_distribution<T>(from, to)(rng);
}

template <typename T>
T rnd_helper(T from, T to, false_type) {
  return uniform_real_distribution<T>(from, to)(rng);
}

template <typename T>
T rnd(T from, T to) {
  return rnd_helper(from, to, is_integral<T>{});
}

template <typename A, typename B, typename Cmp>
bool set_min(A &x, B const &y, Cmp &&cmp) {
  if (cmp(y, x)) {
    x = y;
    return true;
  }
  return false;
}

template <typename A, typename B>
bool set_min(A &x, B const &y) {
  return set_min(x, y, less<typename common_type<A, B>::type>{});
}

template <typename A, typename B>
bool set_max(A &x, B const &y) {
  return set_min(x, y, greater<typename common_type<A, B>::type>{});
}

#include <ext/pb_ds/assoc_container.hpp>

using namespace __gnu_pbds;

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,
                         tree_order_statistics_node_update>;

template <typename K, typename V>
using ordered_map = tree<K, V, less<K>, rb_tree_tag,
                         tree_order_statistics_node_update>;

//  https://codeforces.com/blog/entry/62393
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }

  size_t operator()(uint64_t x) const {
    static const uint64_t
        FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
    return static_cast<size_t>(splitmix64(x + FIXED_RANDOM));
  }
};

#ifdef __cpp_deduction_guides
template <typename F>
struct rec_fun {
  F fun;

  rec_fun(F&& fun_) : fun(std::forward<F>(fun_)) {}

  template <typename... Args>
  decltype(auto) operator()(Args&&... args) const {
    return fun(*this, std::forward<Args>(args)...);
  }
};
#endif

#ifdef __cpp_inline_variables
template <typename T>
inline constexpr auto type_min = numeric_limits<T>::min();

template <typename T>
inline constexpr auto type_max = numeric_limits<T>::max();
#endif

//  fast alloc
#if 0
int const MAX_MEM = 1e8;
int mpos = 0;
char mem[MAX_MEM];
void* operator new(size_t n) {
  mpos += n;
  return (void*)(mem + mpos - n);
}
void operator delete (void*) noexcept {}
#endif

//  pragmas
#if 0
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4")
#pragma GCC optimize("unroll-loops")
#endif

int main() {
#ifdef GOLIKOV
  assert(freopen("in", "rt", stdin));
  auto _clock_start = chrono::high_resolution_clock::now();
#endif
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int const MOD = (int) 1e9 + 7;
  auto add_self = [](int& x, int y) {
    x += y;
    if (x >= MOD) {
      x -= MOD;
    }
  };
  auto add = [&](int x, int y) {
    add_self(x, y);
    return x;
  };
  auto sub = [](int x, int y) {
    x -= y;
    if (x < 0) {
      x += MOD;
    }
    return x;
  };
  auto mul = [](i64 x, int y) {
    return (int) (x * y % MOD);
  };
  int const N = 400;
  vector<vector<int>> pw(N + 1, vector<int>(N + 1));
  for (int base = 0; base <= N; ++base) {
    pw[base][0] = 1;
    for (int deg = 1; deg <= N; ++deg) {
      pw[base][deg] = mul(base, pw[base][deg - 1]);
    }
  }
  vector<vector<int>> pref(N + 1, vector<int>(N + 2));
  for (int deg = 0; deg <= N; ++deg) {
    for (int base = 0; base <= N; ++base) {
      pref[deg][base + 1] = add(pref[deg][base], pw[base][deg]);
    }
  }
  auto get_sum = [&](int deg, int l, int r) {
    return sub(pref[deg][r + 1], pref[deg][l]);
  };
  int n, c;
  cin >> n >> c;
  vector<int> l(n), r(n);
  for (auto& x : l) cin >> x;
  for (auto& x : r) cin >> x;
  vector<int> dp(c + 1);
  dp[0] = 1;
  for (int i = 0; i < n; ++i) {
    vector<int> new_dp(c + 1);
    for (int pr = 0; pr <= c; ++pr) {
      for (int get = 0; get + pr <= c; ++get) {
        add_self(new_dp[pr + get], mul(dp[pr], get_sum(get, l[i], r[i])));
      }
    }
    dp = move(new_dp);
  }
  cout << dp.back() << '\n';

#ifdef GOLIKOV
  cerr << "Executed in " << chrono::duration_cast<chrono::milliseconds>(
      chrono::high_resolution_clock::now()
          - _clock_start).count() << "ms." << endl;
#endif
  return 0;
}


Measured memory_bytes: 1536