Raymond B. answered 06/22/21
Math, microeconomics or criminal justice
Unit cost is the Average Cost
Minimum Average Cost is where marginal cost = average cost
total cost = average cost times quantity. if x is the quantity produced, TC =AC times x
take the Average cost function (the per unit cost function), multiply it by x to get TC, the take the derivative which is the marginal cost. Set the marginal cost = average cost and solve for x
Best I can make of what you've written is
the average cost function might be: AC = C(x) = -0.4x^2 + 96x + 16,541 where 16,541 is the fixed cost and -04x^2 +96x is the average variable cost. But maybe you really gave us the total cost function. the numbers are run together in manner that doesn't makes sense
If that is AC, the TC = -0.4x^3 + 96x^2 + 16,541x take the derivative to solve for marginal cost: MC = TC' = -1.2x^2 + 192x + 16.541
set MC = AC
-0.4x^2 + 96x + 16541 = -1.2x^2 + 192x + 16541
0.8x^2 - 96x = 0
factor
.8x(x - 120) = 0
set the factors equal to zero to solve for x
x-120 = 0
x= 120 is the average cost minimizing output level
plug it back into the original C(x) function
C(120) = -0.4x^2 + 96x + 16,541 = -0.4(120)^2 + 96(120) + 16,541
= -0.4(14400) + 11520 + 16541
= -5760 + 28061
= $22,301 = minimum per unit cost
Just a stab in the dark for a solution, trying to decode the way you've written the problem. It does seem to come out to an integer solution, which is a small clue at least, maybe it's right.