Let g(t) denote the inner integral. By the fundamental theorem of calculus, the first derivative is

Then using the FTC again, differentiating g gives

For these types of problems, plug the value inside the ( ) into the (x) of the equation.
g (-3), g (x) = 2x-2
g (x) = 2 (-3) - 2 = -6 - 2 = -8
g (-3) = -8
Short answer:
TotalCost = 12.96
Long answer:
It gives you the equation of
total cost = C + 0.08C
You just need to plug-in the $12 to the equation.
In other words, the equation is:
TotalCost = 12 + 0.08*12
TotalCost = 12 + 0.96
TotalCost = 12.96
200% bc it went up 2x as much as it cost before
The greatest common factor of those numbers is 8.