Give the starting value $a$, the growth/decay rate $r$, and the continuous growth/decay rate $k$. If there is exponential decay your growth rates should negative. For help entering logarithms, see help (logarithms)

$Q = 0.31 \cdot (4)^t$ has:

$a =$ help (numbers)
$r =$ help (numbers)
$k =$ help (numbers)