#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <numeric>
#include <utility>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <unordered_map>
using namespace std;

#define REP(i, s) for (int i = 0; i < s; ++i)
#define ALL(v) (v.begin(), v.end())
#define COUT(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl
#define EACH(i, s) for (__typeof__((s).begin()) i = (s).begin(); i != (s).end(); ++i)

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T1, class T2> ostream& operator << (ostream &s, pair<T1,T2> P)
{ return s << '<' << P.first << ", " << P.second << '>'; }
template<class T> ostream& operator << (ostream &s, vector<T> P)
{ for (int i = 0; i < P.size(); ++i) { if (i > 0) { s << " "; } s << P[i]; } return s; }
template<class T> ostream& operator << (ostream &s, vector<vector<T> > P)
{ for (int i = 0; i < P.size(); ++i) { s << endl << P[i]; } return s << endl; }
template<class T> ostream& operator << (ostream &s, set<T> P)
{ EACH(it, P) { s << "<" << *it << "> "; } return s << endl; }
template<class T1, class T2> ostream& operator << (ostream &s, map<T1,T2> P)
{ EACH(it, P) { s << "<" << it->first << "->" << it->second << "> "; } return s << endl; }

inline long long mod(long long a, long long m) { return (a % m + m) % m; }
struct Fp {
	int MOD = 1000000007;
	long long val;

	Fp() : val(0) {}
	Fp(long long val_) { this->val = mod(val_, MOD); }
	Fp operator = (long long val_) { this->val = mod(val_, MOD); return *this; }
	inline Fp operator - () { return mod(-val, MOD); }
	inline const Fp& operator += (const Fp &x);
	inline const Fp& operator -= (const Fp &x);
	inline const Fp& operator *= (const Fp &x);
	inline const Fp& operator /= (const Fp &x);
};

inline bool operator == (Fp x, Fp y) { return x.val == y.val; }
inline bool operator != (Fp x, Fp y) { return !(x == y); }

ostream &operator << (ostream &os, Fp x) { return os << x.val; }
istream &operator >> (istream &is, Fp &x) { is >> x; return is; }

inline Fp operator + (Fp x, Fp y) { return mod(x.val + y.val, x.MOD); }
inline Fp operator - (Fp x, Fp y) { return mod(x.val - y.val, x.MOD); }
inline Fp operator * (Fp x, Fp y) { return mod(x.val * y.val, x.MOD); }
inline Fp operator / (Fp x, Fp y) {
	long long a = y.val, b = x.MOD, u = 1, v = 0;
	while (b) {
		long long t = a / b;
		a -= t*b; swap(a, b);
		u -= t*v; swap(u, v);
	}
	return x * u;
}
inline Fp abs(Fp a) { return a; }
inline Fp fpow(Fp a, long long n) {
	if (n == 0) return Fp(1);
	Fp t = fpow(a, n / 2);
	t = t * t; if (n & 1) t = t * a;
	return t;
}
inline const Fp& Fp::operator += (const Fp &x) { *this = *this + x; return *this; }
inline const Fp& Fp::operator -= (const Fp &x) { *this = *this - x; return *this; }
inline const Fp& Fp::operator *= (const Fp &x) { *this = *this * x; return *this; }
inline const Fp& Fp::operator /= (const Fp &x) { *this = *this / x; return *this; }

int N, C;
int A[510], B[510];

Fp sum[510][510];
Fp dp[510][510];

Fp solve() {
	for (int j = 0; j < 500; ++j) {
		sum[0][j] = 0;
		for (int i = 1; i < 500; ++i) {
			sum[i][j] = sum[i - 1][j] + fpow(i, j);
		}
	}
	
	for (int i = 0; i < 500; ++i) for (int j = 0; j < 500; ++j) dp[i][j] = 0;
	dp[0][0] = 1;
	for (int i = 0; i < N; ++i) {
		for (int j = 0; j <= C; ++j) {
			for (int k = 0; k <= j; ++k) {
				dp[i + 1][j] += (sum[B[i]][k] - sum[A[i] - 1][k]) * dp[i][j - k];
			}
		}
	}
	return dp[N][C];
}

int main() {
	while (cin >> N >> C) {
		for (int i = 0; i < N; ++i) cin >> A[i];
		for (int i = 0; i < N; ++i) cin >> B[i];
		cout << solve() << endl;
	}
}




Measured memory_bytes: 8320