Answer:
The sales for the store 7 days after the end of the advertising campaign is
$3849.74
Explanation:
From the question we are told that
The daily sales on the end of campaign day is
= $8,500
The daily sales three days after end of campaign day is
= $ 5,100
The usual day sales of the store is
= $ 3,500
Generally the Newton's Law of Cooling (Heating). equation is mathematically represented as
![G_t = G_u+ [(G_o -S_u ) * e^(-(k*t))]](https://img.qammunity.org/2021/formulas/mathematics/college/tl7hutqste5d0o0jsffbasf7se2im0a70e.png)
Here t is the number of day after the campaign ended
Now substituting values to obtain the constant k
For t = 3
![G_3 = G_u + [(G_o -S_u ) * e^(-(k*3))]](https://img.qammunity.org/2021/formulas/mathematics/college/osj4bluzjvj7mln7kiln1wozutdu2eo9pl.png)
![5100 = 3500 [(8500 -3500 ) * e^(-(k*3))]](https://img.qammunity.org/2021/formulas/mathematics/college/4tko0beqjkhs802o7lu1eezy588jqo3st9.png)

=>

=>

=>

So at t = 7
![G_7 = G_u + [(G_o -S_u )] * e^(-(k*7))](https://img.qammunity.org/2021/formulas/mathematics/college/qdyw9gt59m591h3drk49bczzddmjlvlkrs.png)
substituting values
![G_7 = 3500 + [(8500 -3500 )] * e^(-(0.3780*7))](https://img.qammunity.org/2021/formulas/mathematics/college/qmdee72kyqdtqvdjwy8n79g750877ywyaj.png)
$3849.74