import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string;

auto rdsp(){return readln.splitter;}
void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;}
void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);}
void readA(T)(size_t n,ref T[]t){t=new T[](n);auto r=rdsp;foreach(ref v;t)pick(r,v);}

const mod = 10^^9+7;
alias mint = FactorRing!mod;

void main()
{
  int n, c; readV(n, c);
  int[] a; readA(n, a);
  int[] b; readA(n, b);

  auto bm = b.reduce!max, s = new mint[][](bm+1, c+1);
  foreach (x; 1..bm+1)
    foreach (k; 0..c+1)
      s[x][k] = s[x-1][k]+mint(x).repeatedSquare(k);

  auto dp = new mint[][](n, c+1);
  foreach (k; 0..c+1)
    dp[0][k] = s[b[0]][k]-s[a[0]-1][k];

  foreach (i; 1..n)
    foreach (j; 0..c+1)
      foreach (k; 0..j+1)
        dp[i][j] += dp[i-1][j-k]*(s[b[i]][k]-s[a[i]-1][k]);

  writeln(dp[n-1][c]);
}

pure T repeatedSquare(alias pred = "a * b", T, U)(T a, U n)
{
  return repeatedSquare!(pred, T, U)(a, n, T(1));
}

pure T repeatedSquare(alias pred = "a * b", T, U)(T a, U n, T init)
{
  import std.functional;
  alias predFun = binaryFun!pred;

  if (n == 0) return init;

  auto r = init;
  while (n > 0) {
    if (n&1) r = predFun(r, a);
    a = predFun(a, a);
    n >>= 1;
  }

  return r;
}

struct FactorRing(int m, bool pos = false)
{
  version(BigEndian) union { long vl; struct { int vi2; int vi; } } else union { long vl; int vi; }
  alias FR = FactorRing!(m, pos);
  @property static init() { return FR(0); }
  @property int value() { return vi; }
  @property void value(int v) { vi = mod(v); }
  alias value this;

  this(int v) { vi = v; }
  this(int v, bool runMod) { vi = runMod ? mod(v) : v; }
  this(long v) { vi = mod(v); }

  ref auto opAssign(int v) { vi = v; return this; }

  pure auto mod(int v) const { static if (pos) return v%m; else return (v%m+m)%m; }
  pure auto mod(long v) const { static if (pos) return cast(int)(v%m); else return cast(int)((v%m+m)%m); }

  static if (!pos) pure ref auto opUnary(string op: "-")() { return FR(mod(-vi)); }

  static if (m < int.max / 2) {
    pure ref auto opBinary(string op)(int r) if (op == "+" || op == "-") { return FR(mod(mixin("vi"~op~"r"))); }
    ref auto opOpAssign(string op)(int r) if (op == "+" || op == "-") { vi = mod(mixin("vi"~op~"r")); return this; }
  } else {
    pure ref auto opBinary(string op)(int r) if (op == "+" || op == "-") { return FR(mod(mixin("vl"~op~"r"))); }
    ref auto opOpAssign(string op)(int r) if (op == "+" || op == "-") { vi = mod(mixin("vl"~op~"r")); return this; }
  }
  pure ref auto opBinary(string op: "*")(int r) { return FR(mod(vl*r)); }
  ref auto opOpAssign(string op: "*")(int r) { vi = mod(vl*r); return this; }

  pure ref auto opBinary(string op)(ref FR r) if (op == "+" || op == "-" || op == "*") { return opBinary!op(r.vi); }
  ref auto opOpAssign(string op)(ref FR r) if (op == "+" || op == "-" || op == "*") { return opOpAssign!op(r.vi); }
}
