when n=0, d(n)=690. This is the y-intercept
All the functions given in the options are linear functions in the form y=mx+b, then we must find a function with independent term (y-intercept) b=690
The functions with b=690 are the first and third option.
For the slope (m), we can calculate it with 2 points of the table:
n1=0, d(n1)=690
n2=2, d(n2)=560
m=[d(n2)-d(n1)] / (n2-n1)
m=(560-690) / (2-0)
m= (-130) / 2
m=-65
Then the function must be:
d(n)=mn+b, m=-65, b=690
d(n)=-65n+690
Answer: Third option d(n)=-65n+690