Raymond B. answered 08/03/21
Math, microeconomics or criminal justice
C(x) = .4x^2 -60x +2000
C' = .8x -60 = 0
x=60/.8 = 75 = cost minimizing output level
min C = .4(75)^2 -60(75) + 2000
2250 - 4500 + 2000 = -250
minimum cost is negative = a $250 profit
I(x) = 84x -1000
I'(x) = 84
max profit generating output is when I'(x) = C'(x)
84 = .8x -60
.8x = 144
x= 144/.8
x=180
I(180) -C(180) = 84(180) - .4(180)^2 +60(180) -8000
= 144(180) -8000 - 12960
= 25920 - 20960 = $4,960 = max profit when x=180
profit is when P(x)>0 when I(x)>C(x)
84x -1000 > .4x^2 -60x + 8000
0 > .4x^2 -144x +9000
.4x^2 -144x + 9000 > 0
breakeven output level
x = 144/.8 + or - (1/.8)sqr(144^2 -1.6(9000))
x = 180 + or - 1.25sqr(20736 - 14400)
= 180 + or - 1.25sqr6336
= 180 + or - 1.25(79.6) = 180+99.5
x = 279.5, or 80.5
80.5 < x< 279.5 is the domain for a positive profit
the midpoint output level is the profit maximizing output=180
I(75) =84(75)-1000 = 6300-1000= 5300
max profit = 5300--240 = $5,540