Eliminate $-$productions: Example

$S_{0}S$

$SAB$

$A$aAA

$$

$BbBB$

$$

nullable $(G)=\{A,B,S,S_0\}$

Generate new rules:

Remove $-$productions

$S_{0}S|$

$SAB|A|B$

$A$aAA$|aA|a$

$BbBB|bB|b$

equivalent grammars

EXPLAIN THIS QUESTION THE ONE IN THE GREEN PARTS WHY DID WE PUT CROSS TO THEM CAN YOU EXPLAIN IT PLEASE