From the Hasse diagram, it is clear that in the subset { a, c, d, f }
Elements { a, c, d, f } joins at either f or j or h. Hence f, j and h are upper bounds for the subset and among f, j and h,
f is least upper bound
Elements { a, c, d, f } meet at ‘a’. Hence ‘a’ is lower bound. In fact, ‘a’ is greatest lower bound