Question 88
a) A set $A$ of positive integers less than $2000000$ is called good if $2000 \in A$ and $a$ divides $b$ for any $a, b \in A$, $a \lt b$. Find the maximum possible cardinality of a good set.
b) Find the number of the good sets of maximal cardinality.
b) Find the number of the good sets of maximal cardinality.