Answer:
I think the answer is f' (x)=v
X/2 is the same thing as 1/2x
Interest = $572.60 - $560.00 = $12.60
$560 x 6i/12 = $12.60
i = ($12.60 x 12) / ($560 x 6) = 0.045%
The first two rows of coefficients are identical, so by inspection, the determinant is 0.