The size of the tag field in cache memory equals $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$ where n represents the index size and $2$m represents the number of works in cache block.

$30-($n $+$ m $+2)$

$30-$ n $-$ m

$32-($n $+$ m$)$

$32-($n $+$ m $-2)$