The distribution of Y ( \\ displaystyle Y ) has no closed - form expression .
The distribution of Y ( \\ displaystyle Y ) can be reasonably approximated by another log - normal distribution Z ( \\ displaystyle Z ) at the right tail .
The distribution of Y ( \\ displaystyle Y ) has no closed - form expression , but can be reasonably approximated by another log - normal distribution Z ( \\ displaystyle Z ) at the right tail .