Let $S_k$ be the set containing $2$ and $5$ and the first $k$ primes that end in $7$. For example, $S_3=\{2,5,7,17,37\}$.

Define a $k$-Ruff number to be one that is not divisible by any element in $S_k$.

If $N_k$ is the product of the numbers in $S_k$ then define $F(k)$ to be the sum of all $k$-Ruff numbers less than $N_k$ that have last digit $7$. You are given $F(3)=76101452$.

Find $F(97)$, give your answer modulo $1000000007$.