How to search for common values in a 2 dimensional list and a simple list?

Question

A = [2,7,85,4]
B = [[1,33,6],[3,5,7,6],[1,85,77]]
The idea is to see which numbers are common in those two lists and how many, if you also could explain how to search for common values in 2 two dimensional lists that would be awesome.
Meaning:
A = [[…..],[…..],[….]]
B = [[…..],[….],[…..]]

Answer 1

Flatten the list

Answer 2

Oma Falk actually the list shouldnt be flattened,i need to know how many common values each sublist in B has in common with the A list.