Scenario $2$: Alex seeks to minimize total space $($cost$)$ occupied by chosen items, under total$-$benefit constraints

Objective: Alex seeks to minimize total space $($cost$)$ occupied by chosen items.

Min${\displaystyle \underset{i=1}{\overset{12}{}}}(x_i{c}_i)$

Constraints: Total benefit $($satisfaction$)$ of chosen items should exceed some threshold, $U.$

${\displaystyle \underset{i=1}{\overset{12}{}}}(x_i{r}_i)U$

So which items should Alex choose?