use std::str::FromStr;
use std::io::*;
use utils::*;

pub fn main() {
    let i = stdin();
    let mut o = Vec::new();
    run(i.lock(), &mut o);
    stdout().write_all(&o).unwrap();
}

fn run<R: BufRead, W: Write>(i: R, o: &mut W) {
    let mut i = AtRead::from(i);
    let (n, c) = i.read2::<usize, usize>();
    let a = i.read_vec::<usize>(n);
    let b = i.read_vec::<usize>(n);

    writeln!(o, "{}", solve(n, c, &a, &b)).unwrap();
}
fn solve(n: usize, c: usize, a: &[usize], b: &[usize]) -> usize {
    let min_a = *a.iter().min().unwrap();
    let max_b = *b.iter().max().unwrap();
    let mut pows = vec![vec![ModNum(0); c + 1]; max_b + 1];
    for i in min_a..max_b + 1 {
        let mut value = ModNum(1);
        for j in 0..c + 1 {
            pows[i][j] = value;
            value *= i;
        }
    }
    let mut t = vec![ModNum(0); c + 1];
    let mut xi_pow = vec![ModNum(0); c + 1];
    t[0] = ModNum(1);
    for i in 0..n {
        for j in 0..c + 1 {
            let mut value = ModNum(0);
            for x in a[i]..b[i] + 1 {
                value += pows[x][j];
            }
            xi_pow[j] = value;
        }

        for j in (0..c + 1).rev() {
            let mut value = ModNum(0);
            for k in 0..j + 1 {
                value += t[k] * xi_pow[j - k];
            }
            t[j] = value;
        }
    }
    t[c].0
}

mod utils {
    use super::*;
    use std::ops::*;

    pub struct AtRead<R: BufRead> {
        r: R,
        s: String,
    }

    macro_rules! fn_read {
        {$f:ident($($v:ident: $t:ident),*)} => {
            pub fn $f<$($t: FromStr),*>(&mut self) -> ($($t),*) {
                let i = &mut self.read_line().split(' ');
                $(
                    let $v = next(i);
                )*
                ($($v),*)
            }
        };
    }

    impl<R: BufRead> AtRead<R> {
        pub fn from(r: R) -> Self {
            AtRead {
                r: r,
                s: String::new(),
            }
        }
        pub fn read_line(&mut self) -> &str {
            self.s.clear();
            self.r.read_line(&mut self.s).unwrap();
            self.s.trim()
        }

        fn_read! { read2(v1: T1, v2: T2) }

        pub fn read_vec<T: FromStr>(&mut self, n: usize) -> Vec<T> {
            self.read_line()
                .split(' ')
                .take(n)
                .map(|x| x.parse().ok().unwrap())
                .collect()
        }
    }

    fn next<'a, T: FromStr, I: std::iter::Iterator<Item = &'a str>>(i: &mut I) -> T {
        i.next().unwrap().parse().ok().unwrap()
    }

    const MOD_BASE: usize = 1000000007;

    #[derive(Debug, Clone, Copy)]
    pub struct ModNum(pub usize);

    impl ModNum {
        pub fn new(n: usize) -> Self {
            ModNum(n % MOD_BASE)
        }
    }

    macro_rules! modnum_op {
        (($ot:ident, $f:ident), ($ot_a:ident, $f_a:ident), $($rhs:ty, $e:expr,)*) => {
            $(
            impl $ot<$rhs> for ModNum {
                type Output = Self;
                fn $f(self, rhs: $rhs) -> Self {
                    Self::new(($e)(self, rhs))
                }
            }
            impl $ot_a<$rhs> for ModNum {
                fn $f_a(&mut self, rhs: $rhs) {
                    *self = Self::new(($e)(*self, rhs))
                }
            }
            )*
        }
    }

    modnum_op!(
        (Add, add),
        (AddAssign, add_assign),
        ModNum,
        |l: ModNum, r: ModNum| l.0 + r.0,
        usize,
        |l: ModNum, r: usize| l.0 + r,
    );

    modnum_op!(
        (Mul, mul),
        (MulAssign, mul_assign),
        ModNum,
        |l: ModNum, r: ModNum| l.0 * r.0,
        usize,
        |l: ModNum, r: usize| l.0 * r,
    );

    modnum_op!(
        (Sub, sub),
        (SubAssign, sub_assign),
        ModNum,
        |l: ModNum, r: ModNum| MOD_BASE + l.0 - r.0,
        usize,
        |l: ModNum, r: usize| MOD_BASE + l.0 - r,
    );

}


Measured memory_bytes: 4352