The future value that accrues when $$900$is invested at$9\%,$ compounded continuously, is

S$($t$)=900$e$0\mathrm{.}09$t

where$$t$$is the number of years. $($Round your answers to the nearest cent.$)$

$($a$)$ At what rate is the money in this account growing when$$

t$=4?$

$$$per year

$($b$)$ At what rate is it growing when$$

t$=10?$

$$$per year