Determine whether the following two regular expressions are equivalent or not. And explain

why if not equal?

$($a$)($r$1+$ r$2)$r$2($r$1+$ r$2)+($r$1+$ r$2)$r$1($r$1+$ r$2)$ and $($r$1+$ r$2)($r$1+$ r$2).$

$($b$)($r$1+$ r$2)$r$2$r$1($r$1+$ r$2)+$ r$1$r$2$and $($r$1+$ r$2).$

$($c$)$ r$1$r$2($r$1+$ r$2)$ and $($r$1+$ r$2)$r$2($r$1+$ r$2).$

$($d$)($r$1+$ r$2)$ and r$1($r$2$r$1+$ r$1)$