So I've been studying about complemented lattices and I came across this example.
Determine the complement of a and c
The answer given is that,
a has d as the complement but the complement of c does not exists.
Why is that? Isn't b the complement of c?
Isn't it clear from the diagram that $b \land c=o$ and $b \lor c=I?$
I'm totally new to this, so shedding some light on this dilemma is much appreciated.