Answer:
a) Average price per unit = 700 
b) average marginal cost = -1.5 dollars/frame
c) For 201 frames are produced = $698.5
Explanation:
Given Data: 
C(x) = 60000 + 400x
a) Average cost for 200 units: 
Total Cost of 200 units will be: 
C(200) = 60000 + 400(200)
C(200) = 140,000
Total Cost of 200 units = 140,000
Average price per unit = Total Cost / number of units 
Average price per unit = 140,000/200
Average price per unit = 700 
b) Marginal Average Cost: 
We know that marginal cost =  (x)
(x)
And the average marginal cost =  
 
So, 
 = the derivative of ( )
)
= the derivative of ( )
)
=  + 0
 + 0 
So, 
average marginal cost = 
at x = 200 units
average marginal cost = 
average marginal cost = -1.5 dollars/frame
c) Average cost per frame if 201 frames are produced: 
We already seen in the part b that, the average marginal cost is decreasing by 1.5 dollars /frame. So, 
if 201 frames are produced the instead of 200 then the difference is of 1 frame and we discussed that average marginal cost of 1 frame is decreasing at 1.5 dollars per frame. 
So, 
As we know the average cost from part a = 700 dollars. 
Therefore, for 201 item = 700 dollars -1.5 dollars 
For 201 frames are produced = $698.5