Answer:
1.
(a) The Domain is the set of inputs of the function.
Considering that the function takes a period of 3 weeks (21 days), the domain is [0, 21], once we can't evaluate what happens after the 21st day.
[tex]\text{Domain is } [0, 21][/tex]
Otherwise, it could be [tex][0, \infty)[/tex]
Note: We include 0 and 21.
Once the greatest balance was $400, it will not exceed $400, either it doesn't show negative values.
[tex]\text{Range is } [0, 400][/tex]
Note: We include 0 and 400.
(b)
Once the greatest balance was $400, when x=0, it seems that the y-value is half of $400, therefore, approximately $200. It also represents the initial value, the amount of money when she opened the account.
(c)
[tex]f(x)=B(d)[/tex]
[tex]B(12)=0[/tex]
(d)
It is in segment 4.
The balance equal to zero means that the y-value of the graph is zero, therefore in the x-axis.
