For each molecular formula below, draw a valid Lewis structure $($bond$-$line structure also fine$).$ Each atom should be neutral and obey the octet rule. Include lone electron pairs where applicable. It will be helpful to determine the degrees of unsaturation first. $(3$pts for each valid structure$).$

$($a$)C_{3}BrN$

$($b$)C_2{H}_{4}S$