$($a$)$ Calculate the buoyant force on a $2\mathrm{.}90$ L helium balloon.

$0\mathrm{.}03623$ N $($upward$)$

$($b$)$ Given the mass of the rubber in the balloon is $1\mathrm{.}10$ g$,$ what is the net vertical force on the balloon if it is let go$?$ You can neglect the volume of the rubber.

$0\mathrm{.}02079$ N $($upward$)$