I'm trying to do solve some question from the actuarial exam. The task is to map a function with a graph. In the graph the function is increasing on $[0,80]$ and decreasing on $[80,100]$. The options I can choose from are : $l\_x,\ l\_x^2,\ u\_x,\ l\_x u\_x$. The first two can't be correct because they are decreasing everywhere. What can we tell about the $u\_x$?