#include <iostream>
#include <list>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <map>
#include <chrono>
#include <math.h>
using namespace std;

using lli = long long int;
using Vint = std::vector<int>;
using Vlli = std::vector<lli>;
using Wint = std::vector<Vint>;
using Wlli = std::vector<Vlli>;
using Vbool = std::vector<bool>;
using Wbool = std::vector<Vbool>;
using pii = std::pair<int, int>;
using pll = std::pair<lli, lli>;
template <class T>
using Vec = std::vector<T>;

constexpr int MOD = 1e9 + 7;
constexpr int INFi = 2e9 + 1;
constexpr lli INFl = (lli)(9e18) + 1;
const vector<pii> DXDY = {std::make_pair(1, 0), std::make_pair(-1, 0), std::make_pair(0, 1), std::make_pair(0, -1)};
constexpr char BR = '\n';

#define DEBUG(x) std::cerr << #x << " = " << x << '\n';
#define FOR(i, a, b) for(int (i) = (a); (i) < (b); ++(i))
#define FOReq(i, a, b) for(int (i) = (a); (i) <= (b); ++(i))
#define rFOR(i, a, b) for(int (i) = (b); (i) >= (a); --(i))
#define FORstep(i, a, b, step) for(int (i) = (a); i < (b); i += (step))
#define REP(i, n) FOR(i, 0, n)
#define rREP(i, n) rFOR(i, 0, (n-1))
#define vREP(ele, vec) for(auto &(ele) : (vec))
#define vREPcopy(ele, vec) for(auto (ele) : (vec))
#define SORT(A) std::sort((A).begin(), (A).end())
#define RSORT(A) std::sort((A).rbegin(), (A).rend())
// 座標圧縮 (for vector) : ソートしてから使うのが一般的 ; SORT(A) => COORDINATE_COMPRESSION(A)
#define COORDINATE_COMPRESSION(A) (A).erase(unique((A).begin(),(A).end()),(A).end())



template <class T> inline int argmin(std::vector<T> vec){return min_element(vec.begin(), vec.end()) - vec.begin();}
template <class T> inline int argmax(std::vector<T> vec){return max_element(vec.begin(), vec.end()) - vec.begin();}
template <class S, class T> inline void chmax(S &a, T b){if(a < b) a = b;}
template <class S, class T> inline void chmin(S &a, T b){if(a > b) a = b;}
template <class T> inline void reverseSORT(Vec<T> &Array){
  std::sort(Array.begin(), Array.end(), std::greater<T>());
}
inline int BitI(int k){return 1 << k;}
inline lli BitL(int k){return 1LL << k;}
inline void putsDouble(double d){printf("%.16lf\n", d);}
inline int toInt(const string &s){int res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
inline long long int toLong(const string &s){lli res = 0; for(char a : s) res = 10 * res + (a - '0'); return res;}
template <class T> inline std::string toString(T n){
  if(n == 0) return "0";
  std::string res;
  if(n < 0){n = -n;while(n != 0){res += (char)(n % 10 + '0'); n /= 10;}
  std::reverse(res.begin(), res.end()); return '-' + res;}
  while(n != 0){res += (char)(n % 10 + '0'); n /= 10;} std::reverse(res.begin(), res.end()); return res;
}

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~






int main(void){
    int n, C; scanf("%d%d", &n, &C);
    /* まず, 部分点解法を考えてみる
       f(X) = ∑_{∑ak = C} x_1^a1 * x_2^a2 * ... x_n^an
       f(X) = ∑_{an = 0~C} (∑_{a1+...+a(n-1) = C - an} x1^a1*...*x(n-1)^a(n-1)) xn^an
       したがって, DP[i][j] := ∑_{a1+a2+...ai = j} (x1^a1) * (x2^a2) * ... (xi^ai)
       と定義すると
       DP[0][j] = xj^j
    */
    Vint A(n), B(n);
    vREP(ele, A) scanf("%d", &ele);
    vREP(ele, B) scanf("%d", &ele);
    int maxOfX = 0; vREP(ele, B) chmax(maxOfX, ele);

    // Powers[x][a] := x^a mod 1e9+7
    Wlli Powers(maxOfX + 1, Vlli(C + 1));
    FOReq(a, 0, C) Powers[0][a] = 0;
    FOReq(x, 1, maxOfX){
        Powers[x][0] = 1;
        FOReq(a, 1, C) Powers[x][a] = (Powers[x][a-1] * x) % MOD;
    }
    // S_Powers[x][a] = 1^a + 2^a + ... + x^a
    Wlli S_Powers(maxOfX + 1, Vlli(C + 1));
    FOReq(a, 0, C){
        S_Powers[0][a] = 0;
        FOReq(x, 1, maxOfX){
            S_Powers[x][a] = (S_Powers[x-1][a] + Powers[x][a]) % MOD;
        }
    }
    Wlli DP(n, Vlli(C+1, 0));
    FOReq(a, 0, C) DP[0][a] = (S_Powers[B[0]][a] - S_Powers[A[0]-1][a] + MOD) % MOD;
    REP(i, n-1){
        FOReq(a, 0, C){
            for(int b = 0; b + a <= C; ++b){
                DP[i+1][a+b] += DP[i][a] *
                    ((S_Powers[B[i+1]][b] - S_Powers[A[i+1]-1][b] + MOD) % MOD);
                DP[i+1][a+b] %= MOD;
            }
        }
    }
    printf("%lld\n", DP[n-1][C]);
    return 0;
}

Measured memory_bytes: 4096