# How do I find the GLB and LUB for f-i and f-c for the given lattice?

A labelled image of a lattice.

I am unable to understand how the GLB for i-f will be 'a' (or 0). Since both the points are connected to b and d (which are 2 greatest LBs), in which case it won't even be a lattice.

• You're right: it's not a lattice. Specifically, the meet, or greatest lower bound of $i$ and $f$ doesn't exist; likewise $c \vee f$ doesn't exist either. – amrsa Oct 9 at 21:00
• thank you so much! – Akshat Oct 10 at 8:01