Sara is attempting to develop a new formal logic. The rules are displayed in a similar way as the rules for box$-$proofs $($natural deduction$).$ Brackets are handled naturally. It has the following rules:

X$,$YX$$Y $($the $-$introduction rule$)$

X$$YY$$X$($the $-$rule$)$

X$$YY$$X$($the $-$rule$)$

X$$X $($the$-$ introduction rule$)$

Here is an example of a deduction of the task A$,$B$($A$$B$)($B$$A$)$ in Sara's system:

line $1$: A premise

line $2$: B premise

line $3$: A$$B$-$introduction line $1,$ line $2$

line $4$: B$$A$-$rule line $3$

line $5$: $($A$$B$)($B$$A$)-$introduction line $3,$ line $4$

line $6$: $($A$$B$)($B$$A$)-$ introduction line $5$

Which of the following tasks can be derived in Sara's system?

Question $16$Select one or more: