The sum of pandigital number

In mathematics, a pandigital number is an integer that in a given base B has each digit {0,1,2,3,...,B-1} at least once.

Given two positive integers B and L, let $S(B,L)$ denote the sum of all the L-digit pandigital numbers in base B. For example, $S(3,3)=66$, the sum of four 3-digit pandigital numbers in base 3 is 66 since $(102{)}_3+(120{)}_3+(201{)}_3+(210{)}_3=(2110{)}_3=(66{)}_{10}$

Now we define a new function $H(B,N)={\displaystyle \sum _{L=1}^{N}S(B,L)}$

You are given $H(5,10)=24678960400080$ and $H(123,321)mod1000000007=372652728$

Find $H(12345678,87654321)mod1000000007$

Note: leading zeroes are not allowed.