Given the set a = {0.1.2}. B = {1. M} if a ∩ B = B, what is the direct of real number m Come back quickly

Given the set a = {0.1.2}. B = {1. M} if a ∩ B = B, what is the direct of real number m Come back quickly

A∩B=B,
Then B is a subset of A,
So m = 0 or M = 2