the Here the equation of amount of salt in the barrel at time t is given by
[tex]Q(t)=21(1-e^{-0.06t})[/tex]a
At time t=7 minute the amount of salt will be
[tex]Q(7)=21(1-e^{-0.06\times7})\Rightarrow Q(7)=21\times0.342953\Rightarrow Q(7)=7.20[/tex]The amount of salt after 7 min will be 7.20lb.
b
At time t=14minute the amount of salt will be
[tex]Q(14)=21(1-e^{-0.06\times14})\Rightarrow Q(14)=11.93[/tex]Amount of salt will be 11.93 lb
d
From the graph, for large t the value Q(t) the amount of salt approaches to 21 lb.