Get intersection of arrays in JQ

I'm new to jq,

and would like to get the intersection of two arrays (similar question BUT with different approach: link).I managed to get the union of two arrays and addition of two arrays:i.e:

A=['a','b','e','c']B=['g','a','t','c']

I have wrote:

echo '{"group_a":["A","B","C","ABC"],"group_b":["B","D"]}' | jq .group_a+.group_b

A+B = ['a','b','e','c','g','g','a','t','c']

echo '{"group_a":["A","B","C","ABC"],"group_b":["B","D"]}' | jq .group_a+.group_b | jq 'unique'

A U B = ['a','b','e','c','g','t']

but how do i now apply this simple logic:

intersection = unique((A+B) - (A U B))

i'm used to one liners, and I'd like this snippet to be readable and elegant for future use.so how do i implement this in jq style?

any assistance will be helpful, Thank you all!