In this question ,it is given that
The penny size of a nail indicates the length of the nail. The penny size
d is given by the literal equation

where n is the length (in inches) of the nail.
In the first part we have to solve for n .
And for that firt we add 2 to both sides

Now we divide both sides by 4, that is

Part b.
When d=3

When d =6, we will get

When d =10, we will get

The x intercept represents the initial amount of chocolate bars sold (in this case 0)
Answer:
Step-by-step explanation:
Using formula 
a= 650
b= 800
and c is the unkown