Select all of the true statements from the following,

A bitmap representation of a set has a faster union operation than a hashmap based set

A bitmap representation of a set has a space cost that scales with the number of elements

present in the set

A hashmap based set has a space cost that scales with the number of elements present in the

set

Both hashmap and bitmap based sets allow for constant time $($at least in the common case$)$

tests of set membership

A hashmap set allows for a more efficient set difference operation than a bitmap based set