Let $L=\{a,b,c,d,e,f\}$; $P(L)$ is the set of all partitions of $L$, and $\le$ is the order relation on $P(L)$ defined as:
if $r$ and $t$ are relations, then $r\le t$ iff every block in $r$ is a subset of some block in $t$.
Show that the lattice $(P(L),\le)$ is not modular.