b$)$ Suppose T$1($N $)$ in O $($f $($N $))$ and T$2($N $)$ in O $($f $($N $)).$ Which of the following are true?

$($i$)$ T$1($N $)+$ T$2($N $)$ in O $($f $($N $))$

$($ii$)$ T$1($N $)$ T$2($N $)$ in O $($f $($N $))$

$($iii$)$ T$1($N $)$ T$2($N $)$ in o $($f $($N $))$

$($iv$)$ T$1($N $)$

T$2($N $)$ in O $(1)$

$($v$)$ T$1($N $)$ in O $($T$2($N $))$