Notation for the last X sorted elements of a set I have a set of ages, $\mathbb{T}=\{30, 33, 39, 40, 41\}$.  I'd like to refer to the last $X$ of these ages by $\mathbb{T}^{(X)}$.  So, $\mathbb{T}^{(2)} = \{ 40, 41  \}$.
But how can I define this $\mathbb{T}^{(X)}$?  Somehow I need to communicate, formally, that $\mathbb{T}^{(X)}$ is the subset of $\mathbb{T}$ containing the last $X$ elements of $\mathbb{T}$ when sorted.  

FYI: I'm open to using something other than a superscripted parenthetical numeral if there's something more standard.

Why not define the $\newcommand{\T}{\mathbb T}X$ last number $\T_{(-X)}$ like this
$$
\T_{(-X)}=\max\left(t\mbox{ such that }\#\{s\in\T\ |\ s\geq t\}=X\right)
$$
and then
$$
\T^{(X)}=\{t\in\T\ |\ t\geq\T_{(-X)}\}
$$
