\newproblem{ \begin{problem*}[4]\estraialfa{4}{a,b,c,x,y,z}{element}Let $A=\{\elementi,\elementii,\elementiii\}$ and $B=\{\elementi,\elementiii,\elementiv\}$. \begin{parts} \item \PTs{2} List (without repetition) the elements of the set $A\cup B$ \begin{solution}[3cm] \[A \cup B=\left\{\elementi,\elementii,\elementiii,\elementiv\right\}\] \end{solution} \begin{workarea}{3cm} $A \cup B=$ \end{workarea} \item \PTs{2} List (without repetition) the elements of the set $A\cap B$ \begin{solution}[3cm] \[A \cap B=\left\{\elementi,\elementiii\right\}\] \end{solution} \begin{workarea}{3cm} $A \cap B=$ \end{workarea} \end{parts} \end{problem*} }