import java.io.*;
import java.util.Arrays;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.Function;

public class Main {

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

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        N = sc.nextInt();
        C = sc.nextInt();
        A = sc.nextIntArray(N);
        B = sc.nextIntArray(N);

        System.out.println(solve());
    }

    static int MOD = 1_000_000_007;

    static int solve() {
        // a^c + (a+1)^c + ... b^c
        int[][] S = new int[N][C+1];
        for (int i = 0; i < N; i++) {
            for (int a = A[i]; a <= B[i]; a++) {
                int pow = 1;
                S[i][0] += 1;
                for (int c = 1; c <= C; c++) {
                    pow = mul(pow, a);
                    S[i][c] = add(S[i][c], pow);
                }
            }
        }

        int[][] dp = new int[N+1][C+1];
        dp[0][0] = 1;

        for (int i = 1; i <= N; i++) {
            for (int j = 0; j <= C; j++) {
                // 次数を合わせることを考えてDPをする
                for (int k = 0; k <= j; k++) {
                    // debug(dp[i-1][j-k], "*", S[i-1][k]);
                    int t = mul(dp[i-1][j-k], S[i-1][k]);
                    dp[i][j] = add(dp[i][j], t);
                }

                // debug("dp", i, j, dp[i][j]);
            }
        }

        return dp[N][C];
    }

    static int add(int a, int b) {
        int c = a + b;
        if( c >= MOD ) c %= MOD;
        return c;
    }

    static int mul(int a, int b) {
        long c = (long)a * b;
        if( c >= MOD ) c %= MOD;
        return (int)c;
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
    }

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}


Measured memory_bytes: 26424