#include <bits/stdc++.h>

using namespace std;

const int MOD = 1000000007; // 998244353; // 998244853;

template <typename T>
struct modular {
    constexpr modular() : val(0){}
    constexpr modular(const modular<T>& _m) : val(_m.val) {}
    template <typename U> constexpr modular(const U& _r = U()) {
        val = -MOD <= _r && _r < MOD ? _r: _r % MOD;
        if (val < 0) { val += MOD; } }
    const T operator()() { return val; }
    template <typename U> explicit operator U() const { return static_cast<U>(val); }
    modular<T>& operator+=(const modular<T>& _m) { if ((val += _m.val) >= MOD) { val -= MOD; } return *this; }
    modular<T>& operator-=(const modular<T>& _m) { if ((val -= _m.val) < 0) { val += MOD; } return *this; }
    modular<T>& operator*=(const modular<T>& _m) { val = modular<T>(static_cast<int64_t>(val) * static_cast<int64_t>(_m.val)).val; return *this; }
    modular<T>& operator/=(const modular<T>& _m) {
        T a = _m.val, b = MOD, u = 0, v = 1;
        while (a != 0) {
            T q = b / a;
            b -= q * a; swap(a, b);
            u -= q * v; swap(u, v); 
        } return *this *= u; }
    modular<T>& operator =(const modular<T>& _m) { val = _m.val; return *this; }
    template <typename U> modular<T>& operator+=(const U& _r) { return *this += modular<T>(_r); }
    template <typename U> modular<T>& operator-=(const U& _r) { return *this -= modular<T>(_r); }
    template <typename U> modular<T>& operator*=(const U& _r) { return *this *= modular<T>(_r); }
    template <typename U> modular<T>& operator/=(const U& _r) { return *this /= modular<T>(_r); } 
    template <typename U> modular<T>& operator =(const U& _r) { val = modular<T>(_r).val; return *this; }
    modular<T> operator-() { return modular<T>(-val); }    
    template <typename U> friend bool operator==(const modular<U>&, const modular<U>&);
    friend std::istream& operator>>(std::istream& os, modular<T>& _m) { os >> _m.val; _m *= 1; return os; }
    friend std::ostream& operator<<(std::ostream& os, const modular<T>& _m) { return os << _m.val; }
    template <typename U>
    modular<T> exp(U e) {
        modular<T> res = 1;
        modular<T> b = val;
        if (e < 0) { b = 1/b; e *= -1; }
        for (; e; e >>= 1) {
            if (e & 1) { res *= b; }
            b *= b;
        } return res; }
private:
    T val;
};
template <typename T> inline modular<T> operator+(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T, typename U> inline modular<T> operator+(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T, typename U> inline modular<T> operator+(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) += _rhs; }
template <typename T> inline modular<T> operator-(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T, typename U> inline modular<T> operator-(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T, typename U> inline modular<T> operator-(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) -= _rhs; }
template <typename T> inline modular<T> operator*(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T, typename U> inline modular<T> operator*(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T, typename U> inline modular<T> operator*(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) *= _rhs; }
template <typename T> inline modular<T> operator/(const modular<T>& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T, typename U> inline modular<T> operator/(const modular<T>& _lhs, const U& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T, typename U> inline modular<T> operator/(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) /= _rhs; }
template <typename T> inline bool operator==(const modular<T>& _lhs, const modular<T>& _rhs) { return _lhs.val == _rhs.val; }
template <typename T, typename U> inline bool operator==(const modular<T>& _lhs, const U& _rhs) { return _lhs == modular<T>(_rhs); }
template <typename T, typename U> inline bool operator==(const U& _lhs, const modular<T>& _rhs) { return modular<T>(_lhs) == _rhs; }
template <typename T> inline bool operator!=(const modular<T>& _lhs, const modular<T>& _rhs) { return !(_lhs == _rhs); }
template <typename T, typename U> inline bool operator!=(const modular<T>& _lhs, const U& _rhs) { return !(_lhs == _rhs); }
template <typename T, typename U> inline bool operator!=(const U& _lhs, const modular<T>& _rhs) { return !(_lhs == _rhs); }
typedef modular<int> mint;

// with nomial-coeff
//
//const int N = 410*410; 
//mint dp[2][N];
//
//void solve() {
//    int n, C;
//    cin >> n >> C;
//    int l,r;
//    cin >> l >> r;
//    for (int i = l; i <= r; i++) {
//        dp[0][i] = 1;
//    }
//    int crt = 0;
//    for (int _ = 1; _ < n; _++) {
//        int nxt = crt^1;
//        memset(dp[nxt], 0, sizeof dp[nxt]);
//        int x,y;
//        cin >> x >> y;
//        mint sum = 0;
//        int nl = l+x, nr = r+y;
//        for (int i = nl; i <= nr; i++) {
//            sum += dp[crt][i-x];
//            if (i>y) sum -= dp[crt][i-y-1];
//            dp[nxt][i] = sum;
//        }
//        l = nl; r = nr;
//        crt ^= 1;
//    }
//    mint res = 0;
//    for (int i = l; i <= r; i++) {
//        res += dp[crt][i] * mint(i).exp(C);
//    }
//    cout << res;
//}

const int N = 410; 
mint pw[N][N];
mint sum[N][N];
mint dp[N][N];

void prep() {
    for (int i = 0; i < N; i++) {
        pw[i][0] = 1;
        for (int j = 1; j < N; j++) {
            pw[i][j] = pw[i][j-1] * i;
        }
    }
    for (int j = 0; j < N; j++) {
        sum[j][0] = pw[0][j];
        for (int i = 1; i < N; i++) {
            sum[j][i] = sum[j][i-1] + pw[i][j];
        }
    }
}
void solve() {
    int n, C;
    cin >> n >> C;
    vector<pair<int, int>> a(n);
    for (auto& p: a) {
        cin >> p.first;
    }
    for (auto& p: a) {
        cin >> p.second;
    }

    prep();
    dp[0][0] = 1;
    for (int i = 0; i < n; i++) {
        int l,r;
        tie(l,r) = a[i];
        for (int j = 0; j <= C; j++) {
            for (int k = 0; j+k <= C; k++) {
                dp[i+1][j+k] += dp[i][j] * (sum[k][r] - sum[k][l-1]);
            }
        }
    }
    cout << dp[n][C];
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
    cout << endl;
}


Measured memory_bytes: 2304