Answer:
The cost C as a function of t is C(t) = 30,000 + 6,400,000 t - 40,000 t²
Step-by-step explanation:
The function N(t) = 800 t - 5t², represents the number of cars produced at a time t hours in a day, where 0 ≤ t ≤ 10
The function C(N) = 30,000 + 8,000 N, represents the cost C (in dollars) of producing N cars
We need to find The cost C as a function of the time t
That means Substitute N in C by its function by other word find the composite function (C о N)(t)
∵ C(N) = 30,000 + 8,000 N
∵ N(t) = 800 t - 5 t²
- Substitute N in C by 800 t - 5 t²
∴ C(N(t)) = 30,000 + 8000(800 t - 5 t²)
- Multiply the bracket by 8000
∴ C(N(t)) = 30,000 + 8000(800 t) - 8000(5 t²)
∴ C(N(t)) = 30,000 + 6,400,000 t - 40,000 t²
- C(N(t) = C(t)
∴ C(t) = 30,000 + 6,400,000 t - 40,000 t²
The cost C as a function of t is C(t) = 30,000 + 6,400,000 t - 40,000 t²
and denote the sector area as 
. 
(the ratio between area is the same as the ratio between coresponding angles).
.